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FAQs on Converting Marine to Freshwater Aquarium Set-ups

Related Articles: Setting up a Freshwater Aquarium, Tips for Beginners Aquascaping for Beginners; Twenty Tips for Realistic Aquaria by Neale Monks, Aquascaping Adventures in Aquascaping by Timothy S. Gross

Related FAQs:  FW Set-Up 1

Mmm, some time

Marine to Bathwater Conversion.. for FW, Piranha!        10/26/17
Howzit from South Africa,
<Right backatcha Gar; from S. Cal.!>
After a spot of research on keeping piranha I came across your site, 'bonus'! and thought I'd get your opinion/advice on my future plans.. I currently run a 1'000ltr marine system complete with all it's bits n bobs,
and a 400ltr sump, but unfortunately can't keep up with the maintenance regimen or associated costs. My thoughts are these;
Dump the salt water after removing the inmates and surviving corals Rinse/wash off the existing live rock mainly with the purpose of re-scaping the tank
Fill the tank with tapwater and treat with stabilizers etc.
Allow to cycle for 3-4 weeks
Add a clean-up crew (Pleco, fresh water shrimp, crab, snails etc.)
Considering adding a few black mollies to the sump for future feeding requirement
Add a few plants, and then the piranha.
With this game plan in mind a few assumptions had to be made; The live rock can be re-used in the tropical tank
<I'd switch this and the sand substrate as these are highly likely carbonate based, and will add too much to alkalinity and elevated pH here to be healthful for the livestock you list>
After cleaning the sand substrate in the dt that'll be good to go <Again, I'd sell or store, and replace this with something less reactive.
See WWM re freshwater substrate selection>
The current circulation pump and skimmer will suffice
<Yes; likely so>
I can remove the dsb(deep sand bed) and broken coral chamber in the sump
<Yes I would>
I can remove the 2x chillers and the water should be around 24C- 26C at most
(I'm assuming tropical/piranha are not as dependant on stable temperature as marines)
<They can tolerate a much wider range and fluctuation by and large>
I've been told I can lose the sump, skimmer, and circulation pump, and just put a submerged filter system in my existing Durso chamber, where I could also add a heater or 2 for winter.
<Good ideas; but I'd keep the sump and circulation pump... and likely use or have as back up. The skimmer can go into storage>
So that's about that then, it would be greatly appreciated if you could offer comment and assistance on my master plan.
Kind Regards
Gary
<Thank you for sharing. Please do send along pix, further observations as your project goes forward. Bob Fenner>

Converting Saltwater to Freshwater (Af. Cichlids...)    11/31/14
Hi guys,
Great Site! So I am about to convert my 210g FOWLR tank to an African cichlid tank.
<Easily done... and soooo much easier to maintain!>
The current 210g tank was setup about 14 months ago. I had African cichlids for many years before doing a salt tank but now want to
go back. I would like to note that prior to taking down my tank I ran a 30 day period of Cupramine. in my display tank. After I ran the Cupramine I ran CupriSorb for a month and the Cupramine was successfully removed.
<Ah yes; would have precipitated out by then at any length>
So most of the living organisms in my rock and sand are already dead. So I love the look of my reef rock and would love to keep it.
<Ok; fine to use with most Africans... Great Lakes I take it in your case>
I have already removed the rock and it is sitting in my garage drying. Would it be safe
to let it sit there for a week or two and then just rinse thoroughly add into my tank.
<Yes>
Next question is regarding my sand. There is 160lbs of sand in my display. Can I just drain the tank, stir the sand add freshwater
and reuse it?
<Mmm; can re-use, I would take all out, rinse in aliquots... 5-10 lb.s in a bucket with your hose running>
I would hate to have to by all new sand if its not necessary. Thanks
Erik
<Welcome. Bob Fenner> 

Switched SW to FW (cichlids)      1/22/14
Good Morning,
<Steven>
A week ago, I decommissioned my saltwater 120G aquarium to freshwater. Here is what I did:
13     Jan (Mon night):
*         Scrubbed the aquarium/sump walls as much as possible while draining the saltwater ("SW"),
*         Left 9kg of aragonite sand in the tank as I planned to reuse it again, (I stirred the sand as much as possible while draining the saltwater),
*         Added freshwater ("FW") into 120G and let it run for 1 day,
*         During that period, I removed all my live rocks, skimmer, and rinse the aquaclay to be reuse in FW.
14     Jan (Tues):
*         I tested the salinity of the FW and recorded slight salinity reading of 1.002,
*         Drain all the water from the tank and added back FW, stirred the sand to remove any die offs or debris,
*         Dose Stress zyme bacteria (not sure this works),
<Sometimes... there are (much) better products. Dr. Tim's "One and Only" a fave>
*         Salinity reading is now 0.
15     Jan - 16 Jan:
*         Tank remained cloudy,
*         Ammonia climbed from 0.25 to 0.50, Nitrite  is 0,
*         PH: 7.8,
*         ORP: 350-400,
*         Temperature: 28 degrees C / 83F,
*         During this period, I added bacteria occasionally,
*         Beefed up the amount of aquaclay, modified the sump to have a small trickle filter to accelerate the ammonia conversion,
*         Also read as much as I can, here and other forums.
*         Later did I realised that the overflow compartment had those saltwater living organism (probably dead now, so I scrubbed them) - die offs = ammonia
17 Jan:
*         I added 35kg of white sand (I didn't rinse it) and 40kg of Ryu
rocks
18 Jan:
*         Did a 50% water change once which lowered the ammonia to 0.25
only to climb back up to 0.50 the next day
19 Jan to 21 Jan:
*         Dose Nutrafin cycle and Nutrafin clear
<Nutrafin is not much better/more reliable than the API product>
*         Ammonia is 0.50, Nitrite  is 0,
*         PH: 7.7 - 7.9,
*         ORP: 400,
*         Tank has cleared up a bit but remains cloudy.
Having read the nitrogen cycle can take up to 45days and searches "cloudy tank" on the internet. I do believe I am experiencing a bacteria bloom.
<Agreed>
I reckon that 1 possible pit fall was I should have removed the aragonite sand and rinse it outside before adding to the tank. I wondering if the die off in the sand slowing releasing ammonia? If so I suppose this will prolong my cycling duration?
<Perhaps; but not by much likely>
What should I do now? Continue to perform water changes / dose bacteria?
Can I switch on my UV filter?
<I'd leave off the UV while the system is cycling... And I'd "do" other things to bring about cycling... the better product/bacteria prep. mentioned; adding some established filter media, mulm... Please read here re: http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm
and the linked files at top. Bob Fenner>
Thanks
Voda
Re: Switched SW to FW (cichlids), incl. cycling f'    1/23/14

Hi Bob,
<Steve-o>
Thanks. I did another 50% water change but realize it may not be so good as I am experiencing Heterotrophic bacteria bloom, which will multiple even more.
<They come and they go>
I found some informative websites (true or not, not sure but explains why the products; Cycle and Stress Zyme I am adding is not helping me, as I am adding Heterotrophic bacteria not nitrifying bacteria which are needed to cycle the aquarium)
<Ah yes>
Here's the extract relevant to what I have been dosing:
"Liquid Cycle and Stress-Zyme are just preserved bacteria (mostly Heterotrophs) that are more useful for over feeding or other bio over loads in an established aquarium
Honestly in my tests Cycle or Stress Zyme are really only useful to aid in breakdown of excess wastes from over feeding, poor filtration, etc. (Cycle can also be used as an aid to organic breakdown while waiting for your aquarium Nitrogen Cycle to get started from other means when fish are present).
The Heterotrophic Bacteria within these products can aid in the decomposing of excess organic waste however they are basically useless for actually seeding an aquarium and this is a FACT."
http://www.americanaquariumproducts.com/nitrogen_cycle.html 
Unfortunately Dr. Tim products are not available here and would cost me almost the same price as the product to ship here :(
<Oh; well, time going by then...>
They do have Microbe-Lift Nite Out in the fish shops though.
<Also a worthy product line in my estimation>
Anyway I have added BioDigest vial after changing water last night and asked fish shop to spare me some bio-rings from their filter. Learn couple things today I guess. Lol (lucky i have no fish yet)
Thanks
<And you for your further sharing. BobF>

converting from marine to fresh water 7/29/11
Hi guys
<Hello Ian,>
I have at last decided to change to fresh water. Mainly due to the crazy costs of electricity, fish and corals. Rather than close down completely I thought that converting to fresh water would be a better option in terms of monthly expenses?
<Yes. I recently did a piece for Practical Fishkeeping magazine in the UK on the cost of fishkeeping. I added up the cost of buying a 125-litre (~30 US gal.) aquarium, a heater, filter, and lights; stocking it with community fish and plants; decorating it; and paying for food, water changes and electricity across the next 5 years. The overall cost came out at just over £650, about $1000. Of that, more than half was buying the hardware, with only about £250 coming from running expenses like electricity, and that's over 5 years remember, so that's about £50 a year. The UK is a relatively expensive country, so your own costs may be somewhat less depending on where you live. As it happens, the PFK website used to have a nifty tool for calculating the running costs of your tank. It's still there, but you do need to subscribe to the website, which is free:
http://www.practicalfishkeeping.co.uk/custom/tools/electricity_calculator.php
>
Briefly, I have a 2000L tank with a 700L sump. Water also flows through 2x 100L deep sand bed refugiums. The system runs off 2x Reeflow pumps, one for the main recycling through the skimmer and sump with the other providing the water flow in a closed loop system. Total tank turn over probably about 10x. Two smaller pumps run the skimmer and calc set up. I removed my halogen lamps some time ago and only use T5 tubes. While the Reeflow pumps run more efficiently (than the previous pool pumps) they also generate less heat so now I have a problem in winter with my water dropping to 21C but great for summer at 26C. So the reverse now takes place with me trying to heat the water instead of cooling it in summer!! Back to square one. I also made a decision a year ago to simply stop adding chemicals to the water. Not much changed although to be fair I had stopped buying corals at that stage. Although I have been able to reduce my running costs by about 25% it is still way over the top with this tank costing me about the equivalent of 7000USD a year!
<This does sound rather a lot!>
I would like a colourful tank full of a variety of smaller fish, max 100 mm in size.
<A lot will depend on your water chemistry. Assuming you don't want to go down the avenue of buying or making RO water, then you want species that enjoy or at least tolerate your tap water chemistry. In the case of soft water, pretty much anything from South America, West Africa and Southeast Asia will work, with tetras, Rasboras and barbs being among the more brightly coloured species. In the case of hard water, Central American livebearers, East African lake cichlids, and Australian rainbowfish offer the better options. There is some overlap between the two groups, but for the most part understanding these two sets of water chemistry is the best way forward. If you have middling water chemistry, ~10 degrees dH, pH 7-7.5, then you can mix fish from both sets of water chemistry without problems except in a very few sensitive cases (Mollies for example really need very hard water, while Ram Cichlids don't do well in anything other than very soft water). So, tell me your water chemistry, and we'll discuss further, if you want.>
Plants and various rock or ornaments creating interesting shapes and swim throughs for the fish.
<Strong lighting is useful for the greatest variety of plants, but in all honesty, the importance of carbon dioxide fertilisation in general purpose fishkeeping has been much overrated. If you have something like 1.5-2.5 watts/gallon, or 3-4 fluorescent tubes running the full length of the tank, then in all likelihood pretty much any hardy plant should do well, and a good starting point is Vallisneria and Amazon swords for the background, Anubias and Java fern as specimen plants on bogwood and rocks, and hybrid Crypts and hardy species like Cryptocoryne wendtii for the corners and sides. That's a good mix of undemanding plants that tolerate a broad range of water chemistry and light intensities. You can get a cheap "reef tank" feel by adding small invertebrates -- Cherry Shrimps and Nerite snails are excellent algae-eaters, while Clea helena and Tylomelania snails are fun scavengers and don't breed quickly.>
Since I have "most" of the equipment I imagine that all I have to do is choose the right type of fish and plants to achieve my goal. Could you also indicate which equipment could be used for the new set up.
<Marine-grade skimmers aren't strong enough to work in freshwater, and anything that splashes water, like a trickle filter, will remove CO2 from the water and neutralise the usefulness of CO2 fertilisations. UV sterilizers work as well in freshwater as salt, so you can keep them if you want, perhaps switching on for a couple of weeks after introducing new livestock. Calcareous rock such as tufa and "dead" live rock work fine in freshwater, but will of course raise the pH and carbonate hardness, so are used in seriously hard water situations, livebearers for example, or Tanganyikan cichlids (these latter, incidentally, making excellent alternatives to reef fish, being very similar in shape and habitats -- see for example Neolamprologus leleupi and Neolamprologus tretocephalus. Malawians are good in this context too, but usually a step-up in aggressiveness. Light intensity can usually be half or less compared to an equivalent size reef tank except where the most demanding plants are being grown. Algae is a problem in brightly-lit freshwater tanks, and is best managed through fast-growing plants and algae-eaters, particularly Nerite snails, shrimps and, with care, certain fish.>
Perhaps I am asking for too much but I would like an exciting colourful visual display which is simple to maintain ( I travel a lot) and cheap to run.
Your help would be most appreciated.
Kind regards
Ian
<Cheers, Neale.>
Re: converting from marine to fresh water 7/29/11
Thanks so much for the quick response! Will digest and get back to you.
Many thanks
Ian
<Glad to help. Cheers, Neale.>

Saltwater to Freshwater   3/6/10
Hi WWM:
<Hello!>
I have been an avid reader for many years and really appreciate the site and all that the staff brings in terms of countless pages of great material.
<Thanks for the kind words.>
I am reasonably well read with a decent understanding of the hobby. I have been known to let life get in the way of proper aquarium maintenance at times, and ultimately end up conducting water changes of 20% every 6-8 weeks. I am honest with myself on this issue and need to take this into account. I have had a saltwater tank for the last 5 years (fish with live rock and some inverts like an Anemone and Starfish), but have not been enjoying it of late.
<Oh!>
I have lost too many expensive fish and am interested in getting back to freshwater - something similar to what my Grandfather set me up with many years ago when I was 7. I have a 65 gallon (high) with a 20 gallon sump.
<That's a great size. Lots of potential there.>
I am planning to empty and clean the tank, return the livestock to my LFS, dispose of the sand and keep some of the liverock for the new setup.
<OK.>
My vision is a planted tank with Mollies, Swords and Guppies, maybe some docile small Tanganyika shell dwellers, an appropriate cat and some sort of algae eater.
<Now, while that's a nice list, I will caution you that Swordtails need cooler water the Mollies and Guppies, and Mollies in particular tend to do better in slightly brackish water, unless you can ensure very hard, very basic water with nearly no nitrate. If Mollies are something you're keen on, you might want to choose livestock in such a way you have the option of adding a little marine salt mix to the water, for a specific gravity around SG 1.002. That'd be low enough for plants to do fine, but it will be difficult for soft water fish to adapt to. On the other hand, you could slot in salt-tolerant fish of various types, including some nice catfish and loaches (examples: Hoplosternum littorale and Acantopsis choirorhynchus).>
I have always enjoyed the look of 5 or 6 Corydoras together, but due to the very strong feelings on both sides of the fence I am not sure they would work in this tank.
<Corydoras are great fish, but they aren't an obvious choice for a Molly aquarium, and they also don't like deep tanks, the maximum depth they can be kept at being around 30 cm/12 inches. They're air breathers, and find it very stressful swimming upwards in deeper tanks. The usual recommendation for deeper tanks is Brochis spp., which are very similar, but of course they don't appreciate the addition of salt either, so Mollies and Brochis wouldn't be a good combination. Interestingly, Hoplosternum littorale is a member of the same catfish family, and yet tolerates slightly brackish water very well, coming from such habitats in the wild rather than inland soft water streams. On the other hand, if you went with Swordtails, and kept the tank at 24 C/75 F, you could keep Brochis splendens or the superb Brochis britskii alongside them just fine.>
I will keep the tank with a ph of around 7.5 to 8 with hardwater - I have not yet settled on the appropriate measures. Based on my search of WWM, I think I have enough info on the right types of plants for hardwater, but I am having trouble putting this puzzle together. I am planning to add bioballs to the sump (traditional wet/dry style) as well as some liverock (after I boil it) for PH and hardness support.
<Okay, now, one thing with South American catfish is they tend not to be wild about unusually hard water. So rather than Corydoras or Brochis, you might want to pick your catfish species more carefully. Again, things like Hoplosternum littorale and Megalechis thoracata would be good choices, since both thrive in hard water. Among the African species, you might think about the ones from Lake Malawi and Lake Tanganyika, such as Synodontis multipunctatus or Synodontis petricola, both of which are fairly peaceful by the standards of the genus.>
I am also considering a piece of liverock in the tank - I figure if nothing is alive on it, it should work well in this tank.
<Up to a point, but while stuff is dying, it will add to the nitrate levels, which can cause problems for Mollies. On the other hand, denitrification bacteria will eventually settle on the rocks, improving water quality in the long term.>
I am also unsure of the right substrate that will work for the plants, hardwater and PH in light of not having the most regular water changes.
<Few plants thrive in very hard water aquaria, though there are some that prefer such conditions, including Elodea and Vallisneria.>
All input is appreciated as well as suggestions for other livestock that may enjoy this tank. Thank you in advance for your time.
Mitch
<Cheers, Neale.>

Re: Saltwater to Freshwater  3/11/10
Thank you Neale, or whoever else might be responding today.
<Hello there.>
I own Neale's book, so it is pretty exciting to be able to get advice right from the source.
<Cool.>
I appreciate the feedback and am ready to go, but wanted to get some final feedback on the plan. The tank will be low salinity brackish (1.002), ph neutral substrate that will be plant friendly, like Eco Complete. I will use dead liverock as the biological, placed in a sump.
<This will dramatically raise the pH and carbonate hardness, to levels comparable to those in a Malawi or Tanganyikan aquarium. While that's ideal for some fish and plants, you do need to choose your species carefully, especially the plants.>
I think the use of the liverock along with the marine salt will help keep hardness and ph where they need to be.
<Yes and no. Marine salt mix certainly does raise carbonate hardness, but it also raises salinity, and at least some hard water fish -- Malawian and Tanganyikan cichlids -- seem to resent this. There's a syndrome called Malawi Bloat that seems to be related to the use of salt in tanks with Malawian and Tanganyikan cichlids. Oddly enough Rainbowfish and livebearers don't seem to mind the salt at all, and there are any number of freshwater fish like Horseface Loaches and Ticto Barbs that occur in slightly brackish water too. So precisely why salt adversely affects Malawian and Tanganyikan cichlids is a mystery, to me at least.>
I am thinking about a fair amount of live plants, along with Mollies, guppies, along with a school of rainbows or killifish and some bottom dwellers like the catfish you suggest and Tanganyika shell dwellers.
<Be careful with the Shell Dwellers. While they might be fine at SG 1.002, they might not be. Try a few, see how things go, and if you have problems with them, switch to something else. There are various gobies and killifish that would fit the same sort of niche. Some of these species are tricky to obtain, but if you persist, then species like Chlamydogobius eremius, Redigobius balteatus, Aphanius mento and Adinia xenica are all interesting, attractive species.>
As far as the catfish you suggest, I am having trouble finding them for purchase except the Synodontis which seems quite large.
<On the whole Synodontis aren't good choices for brackish water tanks.
There are some species that do occur in slightly brackish water, like Synodontis batensoda and Synodontis gambiensis, but these are exceptional.
There are any number of catfish that do occur in brackish water, including things like Mystus vittatus normally considered freshwater fish. But on the whole brackish water catfish tend to be large and distinctly omnivorous, putting your smaller fish at risk. If you can keep the Eco Complete under a gravel tidy, and place an inch of soft silica sand, burrower-friendly substrate on top (which you'd have to do for the shell-dwellers anyway) I'd think Horseface Loaches are far better and less dangerous choice.>
All comments and suggestions to the list and setup welcome.
<Cheers, Neale.>

75 gallon aquarium, Salt to Freshwater Conversion 12/29/09
Hello crew I just got a 75 gallon oceanic used aquarium for Christmas and it was used for saltwater well I want it to be freshwater so I washed it out pretty good. The filter, tank and the decorations.
<Ok, you will need to replace all filter media.>
Well I'm not for sure if ALL the salt is out and I want to put albino Corys in it, will they be ok?
<I would clean this tank again and make sure all salt and residual biological material is removed.>
And I set it up about three days ago and it is cloudy now is this normal if so can I put fish in it tomorrow?
<Is normal but no, you cannot add fish until the tank is cycled, otherwise you risk the health/life of your fish. See here for more
http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm .>
Thank you so much!!!!!!
<Welcome>
<Chris>

Converting from saltwater to freshwater Tank Conversion 12/21/2009
Hey Crew. How's it going?
<Hi Aaron>
After the never ending battle of saltwater ich, I think I have decided to go back to freshwater. I have kept freshwater rays in the past with great success and would like another go at it.
<OK>
Is there anything special I need to do as far as the conversion goes.
<Nothing in the tank will cross over.>
My main concern is my tank itself. I have treated with Cupramine and worried it may have some ill effect on a ray.
<Copper is very toxic to rays.>
Any special way to clean the tank?
Empty it out, wash, bleach, rinse and dry the tank. Same thing with the filters.>
And obviously I can not use any of my crushed coral or rocks from the saltwater tank right? I am sure the crushed coral and rock would not be good for his underbelly.
<Correct, they need very smooth sand.>
Anyways, any help on this matter would be greatly appreciated.
Thanks. Aaron.
<MikeV> 

Re: Converting from saltwater to freshwater Tank Conversion 12/23/2009
Ok, do you think it would be ok?
<Should be fine.>
Copper in the sealant wouldn't leach back into the water and hurt my new freshwater inhabitants?
You could run a few Polyfilters in the system before adding any livestock to soak up any copper that might be left in the system.>
<MikeV>

Saltwater to Freshwater Conversion - 10/06/2009
Hi Bob and Crew,
<Hi,>
You have helped me many times in the past with my 90 gallon reef, which I'm thinking about converting to freshwater.
<I see; well, welcome back.>
I started in freshwater and have spent the past 3 years in salt but I'm finding the reef far more time and money consuming to maintain than freshwater.
<This is certainly true to a degree.>
I'm considering switching back to fancy goldfish.
<Worth mentioning: these are more difficult to maintain well, and more expensive to keep clean, than most community tropical fish. Size and their herbivorous habits make them very messy fish. The idea they're cheaper and easier than tropical community fish is a gross mistake, and causes a lot of headaches for people who think they make good beginner's fish. They most certainly do not.>
I'm wondering what the best way to convert the tank is, should I sell it and start over completely or modify to make it work?
<Depends on what you decide to keep. If you're after hard water fish, then things like coral sand and tufa rock could, with some careful cleaning, be used again. If you're into plants, then the lights used for corals work perfectly well for plants. And so it goes on. Decide what you want to keep, and we can discuss further.>
I know the lights will be too powerful and I won't need the UV sterilizer or skimmer. I also have a built in overflow with a very large sump with refugium and I'm looking to simply if I decide to make the switch. Would it be best to still use the sump and add bioballs for the filter or to get some
type of canister filter or hang on?
<A sump is always a good thing to have, no question. Bioballs work as well in freshwater tanks as marine. The big difference is of course you don't usually have live rock for filtration in freshwater tanks (though in theory you could, it's just freshwater live rock isn't sold). So, biological filtration has to be shifted elsewhere. Canister filters, hang-on-the-back filters, and even undergravel filters (especially reverse-flow undergravel filters) all have their place. Since nitrate is usually easy to manage via water changes and/or fast-growing plants, the "nitrate factory" aspect of canister filters isn't such a big deal.>
I believe I need somewhere between 6-10 times the water capacity for gph.
Is that what you recommend?
<Depends on the fish in question. For standard (single-tail Goldfish) and other large, messy fish such as Oscars and Plecs, then yes, turnover rates 6-8 times are preferable. Fancy Goldfish can't swim well, so lower turnover rates, or at least, less turbulent water currents, are desirable, but given their messiness, there's a fine balance to strike between moderate current and clean water.>
Is there one large filter that would be best for this, like a canister, or is using multiple filters better?
<Multiple filters obviously have the plus of redundancy: should one fail, the other is there to keep things going until you buy or fix the other. On the other side of the coin, a single filter will be cheaper to install, and perhaps easier to maintain. On small tanks I personally like to get a single good internal canister filter such as an Eheim Aquaball, and for bigger tanks, I usually have two external canisters. I'm not a huge fan of hang-on-the-back filters, though they work fine with small fish. The problem with big, messy fish is that they have limited capacity for mechanical filter media and usually the inlet and the outlet are close together, causing problems when it comes to circulating water around a big tank. That said, one at each end would work around that problem, I guess.
Reverse-flow undergravel filters are probably the optimal filters if you aren't growing plants that have roots (i.e, no plants, or plants that float or attach to wood).>
The last issue I see is the fact that this tank has a canopy which won't allow me to use the hang on filters and would probably require holes drilled to make the tubes for water coming in and out of a canister filter work.
<Eheim do make jumbo internal canister filters (the "PowerLine" series) designed for use with big fish in big tanks. While pricey, they're extremely well made, last forever, and unlike many budget internal filters, aren't built around space-wasting proprietary modules or worse, chemical media inserts. Two such units should be adequate for a 90 gallon tank (the bigger of the two, the Eheim 2252, is rated at 317 gallons/hour).
Installation would be a breeze, since all you need in the hood is space for the power cable. Maintenance couldn't be simpler, you just pull the filters out, rinse off the media, and stick them back in. You can even plug in additional media compartments if you need to, and by bolting on the spray bar attachment, the water current can be spread out, which will be appreciated by your Fancy Goldfish or any other slow-moving fish (Angels, Fancy Guppies, etc.).>
Thanks for all your help!
<Hope this helps.>
Melissa
<Cheers, Neale.>

Re: Saltwater to Freshwater Conversion - 10/06/2009
Thank you for your suggestions. I have one more question. Would it be a good idea to keep the UV sterilizer I have for my reef to use on the tank when I switch it to freshwater or is it less useful here?
Thanks,
Melissa
<A UV steriliser is certainly useful, and works perfectly well in freshwater aquaria. Cheers, Neale.>

Re: Saltwater to Freshwater Conversion  10/8/09
Hi,
I'm working on the logistics of the tank set up for my 90 gallon goldfish tank. I will use a simple sump with a canister filter or two and the UV sterilizer. I have two questions about this. First, do I need to have a
return pump or can I run the canister filters out of the sump and back into the tank through the canister filter return?
<I would use a separate pump for the sump. For one thing, most canisters won't have pumps strong enough to provide the rate of water flow through the bio-balls you want. Canister filters also need more frequent (ideally, monthly) maintenance than trickle or wet/dry filters, so there's utility in being able to disconnect the canister for servicing while leaving the sump's pump running.>
And do I need to use bioballs or a sock or can I just have the water fall directly into the sump since I will have the canister filter running out of the sump?
<If the sump contains bio-balls, sponges, or whatever, that would be extremely useful and well worth doing. A plain sump filled with just water obviously boosts water volume, and that's helpful. But if you're asking me
should I *either* use just a canister for filtration *or* a canister plus something in the sump/overflow system as well, then yes, the second option is better.>
Also, do I need to use carbon with this type of setup or any other kind of media?
<Carbon is largely redundant in freshwater systems. Weekly water changes are cheap and easy, and should dilute any dissolved organics frequently enough to prevent problems. Since Goldfish like hard, alkaline water, pH drops between water changes should be inhibited by the high carbonate hardness. In general, Goldfish aquaria work best with a generous mix of mechanical media (for faeces and uneaten plant material) and biological media (for the ammonia).>
Thanks again.
Melissa
<Cheers, Neale.>

Converting Marine to Fresh -- 08/06/09
Hi Crew!
<Hello,>
I've been looking through fresh water re: filtration information and I didn't see anything yet about this. I have a very successful Current Nano 12G. It's an AIO with 4 chambers in the back for filtration. I am in the
process of dumping all my corals and fish into a 50G and want to convert the 12G into a fresh and keep a couple of neon tetras.
<OK, but do remember, a "couple" of Neons isn't really fair on these schooling fish. I'd recommend for this tank you got 10-12 Neons, and perhaps half a dozen Cherry shrimps (or similar) as scavenger/algae-eaters.
With good lighting and some plants, this would be rather an attractive and eye-catching system.>
Can I add bioballs and floss to the back chambers and will this be enough for the filtration on this unit?
<Bio-balls and filter floss should be more than adequate for a lightly loaded tank this size, provided the water flow rate was at least 4 times the volume of the tank per hour.>
(After switching out rock and sand of course, removing the 70W MH)
<Indeed. Or you could leave the calcareous media where it is, and keep Tanganyikan shell dwellers.>
Thanks!
Laura
<Cheers, Neale.>

Changing to freshwater and stocking   6/18/08 Hello again. <Hello!> You have all been very helpful in the past with my current marine tank though I now fancy a change as the maintenance of the marine tank is taking up too much time. I have a 500ltr main tank with a 100 ltr sump running an ocean runner 3500. In the main tank I have 2 Hydor no4's to give circulation. The lighting is by was of arcadia series 3 metal halide lamps. <Apart from the skimmer, most of your marine hardware can be used in a freshwater tank with ease. The lights may be rather strong though, i.e., algae-promoting and expensive, unless you're keeping very light-demanding plants. Otherwise, scaling back to the equivalent of 2-3 Watts per gallon fluorescent lighting is ample.> As I mentioned the maintenance of the marine tank is starting to get behind due to time limits and I am looking to switch back to freshwater. That way I can do regular water changes with ease. <Indeed.> So to the point. As I have not had freshwater for a long time I am quite out of it and have tried looking though your articles only to fry my brain. <Oh?> I am looking to use the current set up but change the substrate to a gravel and completely clean out the tanks. If I leave some of the current substrate will this help cycle the tank quicker? <Not really; except in a fairly high-end brackish system, the "marine" filter bacteria will die back completely.> What would you put in the sump for fresh water, I considered just gravel and lots of plants (not sure what type yet) <The usual use for sumps in freshwater tanks is as a place to dump chemical media, specifically carbonate material for raising the KH. This is obviously useful if you're keeping fish that need hard water, such as Tanganyikans, Mbuna, Central Americans, or Livebearers. A brackish water setup would also benefit from the sump being filled with calcareous material, but adding salt to water might be just the sort of work you're trying to avoid! Some (advanced) aquarists also use them as "vegetable filters", using fast-growing plants or algae to remove nitrate from the water. Do look at the book 'Dynamic Aquaria' for info on this sort of thing. Otherwise, simply use the sump as additional filter space and fill with bio-balls or ceramic noodles in media bags.> And finally I am looking for a quite a busy community tank (the kids love watching loads of fishes shoal) but with a few interesting fishes for me. <Lots of options here. If I had a big tank with a sump, I'd definitely explore the idea of small to medium-sized Tanganyikans (lots of colours, interesting behaviour) or "rare" (in the sense of infrequently kept) livebearers such as Goodeids. Both these options would provide ample scope for an advanced aquarist to try out non-standard, non-generic freshwater fish, whilst still offering the family lots of "pretty fish" for them to watch and breed.> Any help on the above points greatly appreciated. P.S. I considered using some of the live rock as decor rock. I know it seems a waste but might as well use some of it as the LFS does not want it all. Will the rock have any benefit in freshwater of just decor. <Dead "live" rock becomes nothing more than limestone rubble; again, splendid for tanks where the fish like hard water, but really rather an expensive approach. Generic tufa rock works just as well.> Many thanks again Paul <Cheers, Neale.> Can I use a saltwater tank for freshwater?  12/18/07 First your site is great. My question is regarding the use of a saltwater tank for freshwater use. I have a 29 gallon tank that was previously used for saltwater, It has sat empty for about 6 months now. Can I use this tank for a freshwater setup? Is there anything I have to do to be able to use this? My LFS said, once used for saltwater, you can't use for freshwater. I would appreciate your input. P.S. Am I still able to use the filters also? Thanks <Hi Dawn. The short answer is yes, a marine tank can work well for freshwater fish. The long answer is that some items used in marine tanks will either fail to work or else will create conditions perhaps not ideal for some species of fish. Of the first sort, protein skimmers are the most important. They will not work in freshwater. Of the second sort, anything that raises hardness, such as coral sand and tufa rock, are useful only in tanks where the fish like hard water. So good with Guppies and Mbuna, but not so good for Neons and Angelfish. Everything else, including filters, lights, heaters will be fine. Cheers, Neale.>

Converting Reef to Cichlid 12/1/2007 Hi Bob and Wet Crew. <Ave!> Hope your all doing well. Its been ages since I emailed you wonderful people. I would like to know what I would have to do to convert my 200 Gallon Reef Tank to a Cichlid Tank? I would also like to know what equipment should I keep in the system. <Does rather depend on the cichlids being kept. If hard water species (Tanganyikan, Malawian, Victorian or Central American cichlids) essentially everything except salt and skimmer will be useful. Soft water species (South American and West African cichlids) obviously don't want limestone materials in the tank like tufa rock. Brackish water cichlids (Chromides, plus various tilapiines and cichlasomines) can be kept tanks more or less identical to marine tanks except the skimmer won't work below SG 1.010).> Tank Info...... 1 200 Gallon Main Tank (Drilled) 2) 45 Gallon Sump with Bio Balls 3 55 Gallon Caulerpa Algae 4) Skimmer 5) UV 6) Heater (I know I should still use this, but just put it as info) 7) Many Powerhead of different specs 8 Denitrifier 9)Many Marine White and Blue Actinic Fluorescent Lighting 10) 2 Pcs Send pumps - 1 x 3325 LitresPH + 1 x 2500 LPH I hope I got everything in there. <Well, obviously the Caulerpa won't work. Better simply freeze it and use as food for herbivorous cichlids. The skimmer won't work except in mid/high-end brackish. UV sterilisers work well in freshwater even though they aren't widely used. Water current is good for riverine/lake-dwelling cichlids, but the blackwater species (like Angels and Discus) won't appreciate too much current. Lighting will be very useful if you keep algae-eating cichlids (Mbuna, Tropheus, etc.) -- allow green algae to grow on all rocky surfaces freely, and these fish will graze it down almost to the rock.> Ghulam <Cichlid care is essentially very similar to marine fish care in terms of requirements for water movement, low nitrates, and in the case of Rift Valley species high levels of carbonate hardness. The big difference is you are more likely to keep groups of the same species, so breeding and social behaviour are greater issues than with marines. Do take care when selecting stock to avoiding having closely related fish: not only are hybrid fry more likely to be produced, but closely related fish often fight more than distantly related ones. There are numerous books on cichlids, and I'd encourage you to have a read of one or two of them before selecting your livestock. Hope this helps, Neale.> Re: Converting Reef to Cichlid   12/2/07 Hi Neale, Wow! This must have been the fastest email reply I ever got in my life! I forgot to mention a couple more things...hope you don't mind :-) I will be keeping Soft Water African Cichlids. What about my Live Rock (seeded from other live rocks now for over 6 years) and live sand/gravel? Shall I just vacuum everything completely? like all the shrimps and worms. Thanks and in Advance for the next email too. Ghulam <The short answer is that you will have to get rid of the sand, gravel, crushed coral, live rock, and anything else calcareous. Soft water cichlids should be kept in tanks that contain only non-soluble rocks, such as slate and granite. I would hope you can sell/give-away the live rock in its "live" condition. It goes without saying that marine live rock cannot survive in freshwater aquaria. Cheers, Neale.>

Freshwater sumps  11/28/2007 Hello again. You have been very helpful so far and I feel bad about pestering you for info but again there seems to be a lack of info on this subject. I am converting from marine to freshwater (most people go the other way) and have a sump which I want to use with this system. The tank is about 500ltrs with a 100 ltr sump. My question (to finally get to the point) is what would you recommend to put in the sump. Currently the first section is bio balls, then miracle mud with colerpera (sorry about the spelling) and finally live rock with a live sand bed. I know the live sand will 'die' and the live rock would be a waste. I was thinking about keeping the bio balls but replacing the mud with gravel and some sort of plants. The main section was to be changes to gravel. Have you any suggestions with what I am proposing. Any help gratefully received. Many thanks Paul. <Hello Paul. Unless you're keeping a hard water aquarium for, say, Tanganyikan cichlids then don't leave anything calcareous in the sump. For a standard community tank or similar, then opting for biological filter media of some type is probably the way forward. More bio-balls or some sponges would work well. Because nitrate control in freshwater systems is both easier (plants, water changes) than in marine tanks and less critical (freshwater fish largely nitrate-tolerant) there's no real need to provide denitrification in a freshwater tank. But some people have very effectively used 'vegetable filters' and 'algal scrubbers' as part of the filtration system, by placing fast-growing plants/algae into a brightly-illuminated chamber. There's a book called "Dynamic Aquaria" that discusses these, among other such esoteric topics. While hardly a book for the casual aquarist, it's an interesting read if your library has a copy. Basically the idea is that you optimise plant/algal growth, and then crop the plants (even daily!) effectively removing wastes in "solid form". Some freshwater plants, such as Cabomba and various floating plants, will grow incredibly rapidly if provided optimal conditions. I hope this helps, Neale.>

Marine to Freshwater.   11/14/07 Hello all. Quick note to great website as ever but am struggling to find my answer so hope you can help. I have run a largish marine set up (500ltr with 100ltr sump) for 2 years and am finding it difficult to find time for the maintenance. I am considering to go back to a fresh water set up but I want to use the existing equipment. Can you let me know if there are any pitfalls with this. <Essentially no problems at all. The main thing is that some systems used in marine tanks either won't work in freshwater or won't be helpful. Protein skimmers stop working below about SG 1.010, and things that drive off carbon dioxide (like trickle filters) won't be appreciated by plants (which want all the CO2 you can give them). Lime-rich materials used for decoration are fine in hard water tanks, e.g., with Mbuna, but can't be used in standard aquaria where neutral or acidic environments are desired.> The sump has miracle mud (though this will be got rid of), bio balls and live rock which is lit. What would you recommend to put in the sump? <Doesn't matter too much. Anything that will support biological filtration will be fine. So go by your budget or whatever appeals to you.> I have T5 lighting that alternates with a 'moon' light for the night time. Would this be ok or too much. <Depends on what sort of fish you are keeping. Some freshwater fish don't like bright light (e.g., Discus). But if you have lots of plants to provide shade, strong lighting is useful. Among other benefits, rapid plant growth suppresses algae and consumes nitrate. Floating plants like Ceratopteris are especially good for this.> I would replace the substrate from fine marine sand to normal gravel (or would you leave alone?). <Depends on the fish. Coral sand or lime-rich sand are fine for hard water tanks. But if you keeping a planted aquarium you need particular iron-rich, slightly dysaerobic substrates for them, and standard community fish wanting a neutral pH need an inert substrate such as silica sand or gravel. So research your stock list and planting ideas, and choose substrate based on that.> Any other problems I might encounter? <None that can't be prevented by research! On the whole, if you've mastered marine fishkeeping, freshwater fishkeeping should present too many problems. The common mistakes -- overstocking, overfeeding, inadequate filtration, etc. -- are identical. Live plants present peculiar problems similar to but different from those of corals. They need light, yes, but they also need CO2 and a nutrient-rich substrate (unless the plants kept are floating plants or epiphytes, in which case substrate is irrelevant). The range of invertebrates is more limited, primarily shrimps and snails, but by contrast with marine tanks, freshwater invertebrates tend to be easy to keep and prone to overpopulation if not watched (I have cherry shrimps breeding at a rate that would make me a billionaire if they were marine cleaner shrimps!). The main difference is really one of specialisation: while virtually all ornamental marine fish are from coral reefs, freshwater fish come from a range of habitats from mountain rapids to swamps to giant lakes to rainforest rivers. All require different sets of conditions. Much of the fun in freshwater fishkeeping comes from specialising in one particular habitat, and collecting fishes and plants typical of that habitat. You can then choose rocks, sand, bogwood and other decorative materials to create the "look" of that place, too. Water-worn boulders and Vallisneria would suggest a fast-flowing Asian river, while Anubias and bogwood roots could be use to create an African swamp. And so on. There are several books out there all about this aspect of the hobby. My favourite is 'The Complete Aquarium' by Peter Scott.> It the moment I have a 10 times water flow. Is that too much for fresh water, should I just use the return pump from the sump (3500ltrs p/h). <My freshwater tank has a similar turnover. It presents no problems to riverine fish that like water current, things like Corydoras, pufferfish, Plecs, midwater barbs and tetras, etc.> Many thanks for any pointers. Paul <I hope this helps, Neale>

Saltwater to Freshwater   5/18/07 Hi folks, great site! <Hello Billy.> I recently purchased a used 55 gallon saltwater tank that I want to use as a freshwater tank. It's your standard 55, 48x12.5x18 (or close, you get the idea). It has 2 Emperor 400 BioWheel Hobs and a Rena XP2 canister. I already removed the crushed coral. The plan is one or two Oscars (I know 55 is pushing it) and a pleco. <Sounds fine so far, though as you seem to realise, all these fish, if not actually huge, are messy, and tend to make small tanks with basic filtration rather murky.> This is the reason I was happy about the amount of filtration. In this area there is one person at one LFS that seems to know some things, and he's hard to catch. Other than that, you have your basic retail help. Very eager to help, just no experience. That's why I came to you guys. <Or better yet, invest in a good aquarium book. There are titles at every price point, and sitting down and reading is time well spent. Your public library will also have a variety if you don't want to buy a book.> I have a few questions about what to do next to convert the tank to freshwater: Will a good rinsing of the tank be sufficient? <Yes. Very few life forms of any kind, beneficial or otherwise, will survive going from marine to freshwater conditions (that's what makes brackish water animals so special). Almost all the bacteria, algae, potential pathogens, etc. will be killed merely by changing the salinity. Throw in a good clean with warm water and a sponge, and you're laughing.> It's actually soaking in the garage now to see if there are any leaks. <Good call.> What about the HOB filters, same? <Yes. Obviously you'll need to re-cycle the filter to get the bacteria back.> I've never used a canister. Is inside the stand, under the tank, ok? <Standard place to put it. BUT, because it is now working against gravity, pushing the water up from the filter into the tank, the pump moves less water. So knock off at least 25% from the stated turnover of the filter to allow for this and a certain amount of clogged filter media.> What if I lose power, will gravity pull the water out of the tank and onto the floor? <Not if you've connected it properly. Switching off the filter will simply stop the water moving. Nothing should leak out. A couple of tips though: Make sure there's a drip loop on the power cable, i.e., the lowest part of the cable between the filter and the power outlet is LOWER than the power outlet, so any dribbling water goes onto the floor not into your mains electrical supply. Secondly, if you're paranoid about leaking water, drill a small hole on the INLET tube in the aquarium an inch or two below the surface of the aquarium. What this will do is break the siphon if a leak develops in the canister filter system, so only the first one or two inches of water can escape from the tank. Any good aquarium book should show you these two tricks.> And same as before, will a thorough rinsing be adequate? What goes into the 2 baskets inside? Any words of wisdom for a nervous canister newbie? <Here's Neale's golden rules of canister filters. [1] Don't use carbon, zeolite, or peat. All three are unnecessary in most freshwater aquaria. [2] Choose a mix of mechanical filter media and biological filter media. [3] Filter wool is excellent for mechanical filtration but needs to be replaced periodically. [4] Good quality sponges or ceramic media are well worth buying because they last for many years. [5] Do a trial run setting up the canister filter with a bucket of water in the back garden or in a sink. The first time you use one you'll find them fiddly, so it's worth figuring out the rubber seals and various taps somewhere an accidental leak won't do any harm. [6] Once set up, leave the filter alone. You only need to clean it very occasionally, certainly no more often than once a month, and some aquarists get by cleaning them once a year. It'll be obvious when water flow is declining, and that's when to clean the filter. [7] If your filter is clogging up within weeks, it's overwhelmed. Either add a second filter, or be more proactive with the hosepipe and bucket, siphoning out detritus on a daily basis if required (this is what I do with my tank with an adult Panaque who could poop for Britain if it was an Olympic sport). [8] Never, ever clean the filter media in anything other than fish tank water.> My plan was to run the filters for a while in the sink to flush them out. <Seems a bit pointless but okay.> It didn't come with any actual inserts (media?), so those will be new anyway, but the tubes, impellers, and are where the filter inserts hang would get a good flushing. <Some filters come with media, some without. Hardly matters really some these are low cost, long lifespan purchases. A box of good quality filter media like Siporax will last ten years or more if looked after properly.> Thanks in advance for any and all help!!!! Billy <No problems. Good luck! Neale>

Marine to freshwater conversion   1/6/07 <<Hello, Jonathan. Tom here.>> I have a 90 gallon FOWLR with a DSB (4' of aragonite sand), 10 gallon refugium, 20 gallon sump, and a closed loop manifold that gives me about 18X circulation rate when I combine the sump return pump.   <<Okay.>> I was always a freshwater keeper but last year built this marine setup and have found myself recently wanting to switch back to the freshwater world. How difficult would it be to switch this setup to freshwater?   <<With a few changes, I don't see this as being a problem at all, Jonathan.>> I understand that the live rock, skimmer, and algae in the refugium would have to go with the fish, but what about the substrate?   <<The aragonite sand would likely be one of the changes you'd have to make unless you intend to keep species requiring a high pH -- in the 8.0+ range, African Rift Lake Cichlids, perhaps. Because of the sand's constant release of carbonate into the water, you'll never get the pH down below what is commonly reserved for FOWLR and reef setups.>> I am interested in a planted tank. Could I pull the substrate and rinse it thoroughly? <<We're still at the issue of pH here, Jonathan. No amount of rinsing will change the sand's natural characteristics. Additionally, this rules out my earlier reference to the Rift Cichlids. Plants won't last a half hour.>> Is the 18X turnover rate too much for a planted setup?   <<I would say so. You probably wouldn't want to exceed 12X with a planted tank and even this depends on what types of plants you want to keep.>> Could I find some beneficial use for the refugium?   <<Depends on how closely you want to stick with the inherent use for a refugium. As you know, these are often used for inverts and delicate species that wouldn't survive in the display tank due to something trying to make lunch of them. Might take some imagination on your part but I wouldn't rule out the possibility of making use of it in a freshwater application. Obviously, since the display and refugium would have identical water parameters, your selections would have to be made accordingly.>> I am only testing the waters, y'all have always been very helpful before.  Thanks for your advice. <<All in all, I don't see this as a bad way to go, Jonathan. It's been quite a while but I spoke with a fellow who laid out a large FW system almost identical to what I picture yours to be. Can't say I recall what his use for the refugium was, unfortunately, but equipment-wise, all he, understandably, lacked was a protein skimmer. All else was a 'saltwater' setup with the exception, of course, of the inhabitants and salt.>> Jonathan <<Good luck with the conversion. I'd be interested in finding out how you go with this. Tom>>

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