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FAQs on Biological Filtration in Freshwater Systems

Related Articles: Establishing Cycling, Freshwater Filtration, Know Your Filter Media, A Concise Guide to Your Options by Neale Monks, Freshwater Deep Sand Beds Work by Deirdre Kylie, Setting up a Freshwater Aquarium, Tips for BeginnersWater Quality and Freshwater Aquariums

Related FAQs:  Establishing Cycling 1, Cycling Products, Freshwater Filtration, Freshwater Environmental Disease Nitrates in Freshwater Aquariums, Ammonia, FW Nitrites, FW Nitrates, Chemical Filtrants,

New platys... beh. in an uncycled sys.    1/2/12
Hello I hope you can help, I have recently bought two ten gallon tanks with gravel, filters etc... We have put the same water in and treated it. Then left the filters on for five days before buying the platys three for each tank, two females one male per tank. The one tank they swim around and are active, the other all hide in the tank behind arches and other items. We rarely see them swim even when food is put in the tank they don't move when were about. On occasion if were out the room and come back one may have ventured out but then immediately hides away. Can you help any ideas or suggestion would be greatly appreciated, we are looking forward to see the platys swimming around. Thank you.
<Hello Tim. Hard to explain the differences here. But 10 gallons is below what I'd recommend for Platies, and they may well simply feel cramped. When that happens, fish act nervously, as if trapped in a puddle too small for them. However, my money would be on a water quality problem. How did you cycle the filters? Understand this: switching a filter on and leaving it running in an empty tank does NOTHING other than make it wet. There MUST be a source of ammonia for filter bacteria to use. If you didn't use an ammonia source for 3-4 weeks before adding the fish, then BOTH of these tanks are cycling with fish in them, and that's hardly ideal. So, you can probably assume non-zero ammonia and nitrite levels, and these can and do make fish act nervously. They feel themselves being "burned" by the ammonia, but can't explain or understand what's happening beyond the fact they feel pain. So they hide away, hoping the "enemy" will go away. Grab a nitrite test kit, and see what the nitrite level is. If it isn't zero, then that's your problem. If you must cycle with fish in place, you need to do 20-25% water changes every 1-2 days for the next 3 weeks. Feed minimally, no more than once every 2-3 days. Only when you register 0 levels of ammonia and nitrite for several days in a row can you switch to normal feeding and weekly water changes. Cheers, Neale.>
Re: New platys   1/2/12

Hi Neale, thanks for your help, I added a bioactive tap safe as per the directions.
<Yes. This removes chlorine, chloramine, copper (and other heavy metals) and tap water ammonia (as distinct from the ammonia that comes from your fish). This product makes tap water safe. That's all.>
Is this what you mean when referring to ammonia?
<No. Ammonia is the stuff filter bacteria "eat". In a mature aquarium, they consume ammonia at the rate the fish excrete it, so the aquarium stays healthy, with a zero level of ammonia. But for the first 4-6 weeks there aren't enough filter bacteria, so you need to cycle (or mature) the aquarium by providing ammonia for filter bacteria to eat. Over time, the populations of bacteria grow. With me so far? Plain tap water contains no ammonia (usually) so we add an ammonia source. Some aquarists add household ammonia, but a simpler approach is to add tiny pinches of flake food, just as if there were fish there, and as the flake decays, it releases ammonia.
Now, you have fish in the tank already, and they're producing ammonia all the time, the same way we produce urea (which ends up in the urine). Unless and until the filter bacteria population is big enough to use it up as quickly as it is made, you'll have ammonia collecting in the water. Daily water changes will dilute this, and feeding fish less will lower levels still further. An ammonia level of 1 mg/l is lethal, and even 0.5 mg/l is enough to cause disease. Feed less, and do more water changes, for around 3-4 weeks and you should find the filter matures without your fish being seriously harmed.>
I have a local pet shop which had offered to test my water tomorrow.
Hopefully this will shed some light on the issue. Then I can start to sort the water as per your directions, thanks
<Cheers, Neale.>

Bio-wheel from a Penguin 150 filter and persistent yellow water in 55G FW  1/3/11
Hello WWM Crew and Happy New Year,
I have a question I would like to submit to you:
How can I preserve a mature bio-wheel from a Penguin 150 filter?
<Not hard.>
I used to have a 20-gallon FW aquarium with the
Penguin, but I upgraded to a 55G with a Cascade 700. I am temporarily keeping the bio-wheel in a container with some aquarium water. I do not have the capacity of keeping both tanks up, but I would love to keep the bio-wheel alive as back up for 'hospital or QT' situations. Should I put the bio-wheel in the 55 g aquarium as 'decoration'?
<Yes, this will work. Anywhere that keeps the media wet, oxygenated, and exposed to an ammonia source -- e.g., fish -- will work just fine and dandy.>
Also, my aquarium water is always yellow.
<Quite normal. Comes from bogwood mostly, and to a much smaller degree to organic decay of plant material, faeces, etc. Activated carbon will remove yellowing, as will regular substantial water changes -- 25% weekly is the standard recommendation. Do remember that carbon needs to be replaced at least every 2 weeks, and the space it takes up in the filter isn't doing biological filtration. Under most situations, carbon is useless, so it's best to leave the filter to biological media, and control yellowing via water changes and/or removal of some or all of the bogwood.>
I have Flo-Max and natural color gravel as substrate for the following plants; Anacharis bunches, Amazon swords, Anubias, a Cabomba; 15 platys, 6 Pristella, 7 Neon Tetras, and 2 Yoyo Botia Loaches. I also found 5 platy fries. I have several natural rocks, light brown in color, some are petrified wood and coming from the 20 G tank (established in November). I do a 10% water change weekly, and scrub the walls gently; I try not to be aggressive in my cleanings. When I test the water with Quick Dip strips these are the levels -- (approximate values as they are on a color chart):
Nitrates within 20,
Nitrites between .5 and 1
<Not good; will eventually stress, kill your fish. Must be zero! The tank is overstocked, under-filtered (perhaps a poor balance of biological media vs. chemical media), and/or the fish are over-fed. Review and act accordingly.>
Ammonia is 0
Chlorine is 0
PH is between 7.8 and 8.4,
GH is 300
KH is 300 also.
I plan on using these strips up and buy the big kit from API, I am not sure I can trust the accuracy of these strips, but the local PetSmart assistant said the were reliable.
<They're good enough. Not as accurate as liquid kits, but easier to use, and if sliced vertically to make two strips from one, very economical. When it comes to nitrite and ammonia, anything above zero is bad, so the precise value doesn't matter too much.>
Any advise?
Many thanks in advance for your input. I really appreciate your time and input.
Sincerely Francesca B
<Cheers, Neale.>
Re: Bio-wheel from a Penguin 150 filter and persistent yellow water in 55G FW  1/5/11

Hi Neale, Thank you for your prompt reply.
<No problem!>
I suspect I tend to over-feed.
<Naughty, naughty'¦>
I will correct that and do 25% water changes instead of 10%.I also want to compliment you and everyone at WWM for the excellent website, the wealth of information, and the time and patience you "guys" have for "us" newbies!
<We're happy to help. Cheers, Neale.>

Sharing information, FW veg. filter input, poss. art.!   4/10/10
You've helped me many times by providing good answers very quickly so I thought I would share a couple things I've done with my aquariums.
I published the pictures I have on Picasa web to save space (your welcome to use them if you like).
<I've put the link at the end of this e-mail.>
The pictures of the plants are lucky Bamboo in a little plastic tub on the back of the tank. I cut a hole in the tub and made a drain using PVC, potted the plants in aquarium rocks and found a cheap little 20gph pump ($15) that pumps water to the tub through plastic airline. I clean it about every six months by pulling out the plants and cleaning all the algae out of the rocks and after two years these plants are still doing quite well. I've read that Lucky Bamboo, which isn't really Bamboo, likes nitrates but even if it that's not true it still looks pretty cool. Lucky
Bamboo, at least in my area, is usually expensive but I found a web site and got everything you see delivered to my door for $20.
<Essentially what you've created is a vegetable filter, quite widely used to clean ponds. Fast-growing plants do indeed absorb nitrate as well as ammonia, so they can do a good job keeping water clean.>
The other pictures are of a common whole house filter ($20) mounted on a 2x6 with a couple bicycle hooks, PVC pipe and an adapter so I can attach and remove a 500gph pond pump ($40). I hang this over the tank, put a 20
micron pleated filter ($1) in it and stir up the tank and let it filter out the particles. If I have an algae bloom, rather than using chemicals I perform a 20-30% water change and put a carbon filter in the canister ($5) and it clears out the tank in about an hour.
<A cheap alternative to a diatom filter, by the sounds of it.>
<Do consider putting together a more step-by-step article on these two ideas for 'Conscientious Aquarist'. Take a look at these examples, here:
Instructions and what we pay are here:
Cheers, Neale>

Re: Sharing information  4/11/10
I will probably give it a shot.
One of the articles was about fresh water sand beds and I'm curious you guys think this is a good idea?
<It can work, certainly.>
I'm trying to come up with a way to lower nitrates without water changes and before this sand bed idea I was thinking of creating my own canister filter using a low flow rate and Seachem Matrix.
<Can't see this working. Water flow wouldn't be slow enough, in my opinion.
The point of deep sand beds is that water movement is extremely slow, essentially marginally above diffusion rates.>
I'd love to your thoughts on these and any other ideas for removing nitrates.
<In freshwater tanks fast-growing plants, especially floating plants, are the easiest approach. In some cases a DSB may be relevant. But in most cases simply doing more water changes is the most cost effective approach.
Unlike the case with saltwater tanks, making water for freshwater tanks isn't expensive, and exposure to small water chemistry changes aren't as big of a deal, so water changes are cheap, safe and easy.>
<Cheers, Neale.>

Re: Sharing information, FW filtr. art. poss.  -- 4/12/10
Now I'm wondering if a DIY coil denitrator is a good way to go. The main problem is the amount of different information about them.
<Do read here:
While this is about saltwater applications, the basics are the same for a freshwater version.>
They seem pretty simple to make but I don't know if they need to be feed at all and is there a danger of it going bad and poisoning the tank.
<Not if built, operated, and maintained correctly.>
I know I can keep doing water changes but it's fun trying to see if I can make a system that will complete the whole nitrogen cycle itself.
<Not really practical so wouldn't think this way. Water changes *are* the way to control nitrate in freshwater systems. Fast-growing plants can also make dramatic reductions in nitrate level by direct absorption. Asking for
ideas "outside" of water changes and plants is rather like saying other
than eating less and doing more exercise, how can I lose weight?>
So outside of recommending water changes which (if any) system for removing nitrates do you think would be the best and the safest, deep sand bed, Denitrator or something else.
<DSBs and porous rocks -- what are called live rock in marine tanks -- have been proven again and again to be the easiest and most cost-effective ways to close the nitrogen cycle in marine tanks. But even there, water changes
are essential. Plus, don't forget that nitrate removal is only part of water changes are about. Water changes also restore carbonate hardness, dilute organic acids, remove tannins, reduce phosphate, and supply trace minerals. If you want to spend your money on something, then consider reducing the nitrate content of the water going into the tank.
This can be an RO system for example, or a rainwater butts under the gutters to collect mineral-free water at zero cost. Either way, mixing nitrate-free water 50/50 with hard tap water is a great way to create water ideal for a wide variety of fish species. I use rainwater mixed with tap water in precisely this way.>
If you happen to recommend something and know of a good DIY link that would help a lot.
Thanks again for being out there to help us amateurs
<Cheers, Neale.>
Re: Sharing information -- 4/12/10
Thank you. I still expect to do water changes but a little less often.
<With freshwater tanks, you're likely to find the cost/benefit ratio makes little sense.>
I live outside the city water supply and am lucky to have a well with 0 nitrates and no other chemicals added. I think I will work on a coil denitrator and more plants.
<Fast-growing plants, or better still algae, can work extremely well for "closed" systems. Do see for example 'Dynamic Aquaria' for discussion of algae scrubbers. In theory and to some extent in practise, you can create
lightly stocked aquaria where the only thing you do is add water to compensate for evaporation. In general though, such tanks are so expensive to set up, and contain so few fish, that they're worthless to hobbyists.
With that said, the benefits to be gained from a clump of Indian Fern growing rapidly under bright lights is substantial, and a sump that turned into an algae scrubber would be even better. Do see the marine literature on the use on these items, for example here:
Thank you again,
<Cheers, Neale.>

pH effect on nitrifying bacteria 3/28/09
I'm setting up a Malawi cichlid aquarium.
<Very nice!>
I intend to inoculate the tank with sponge filter media from a friend's aquarium to begin the cycling process.
<Excellent idea.>
My friend keeps South American cichlids, and his aquarium pH is about 7. My aquarium water (tap water) is about 7.8 and is hard.
<Nothing to worry about.>
I've read that the bacteria may not survive substantial changes in pH when transferred from one system to another.
<Yes, this is true, but if you acclimate the media just as you'd acclimate fish, you'll be fine. In other words, put the media in a bucket and just-cover with water from the South American aquarium. Over the next, say, 30-40 minutes, add a cup or two of water every 5-10 minutes until the bucket is filled. When it's done, that's it! Move the media into your filter, and off you go. As ever though, do take care to check nitrite or ammonia in the days thereafter, and stock the tank slowly, taking care not to overfeed.>
Should this be a concern for me? If so, can you suggest how I could handle the transition? (I don't know anyone with an African tank who could help me.)
Many thanks.
<Good luck, Neale.>

Bacillus Bacteria filtration?  9/27/08 Hello crew, I was reading the following article http://www.wallaquariums.com/cycling.htm and they strongly encourage the use of something called Fritz Zyme #360 Gravel Cleaner. I've done some research on this product and the bacillus bacteria, and I was hoping to get an opinion from a trusted source. I'm brand new to this, and I'd prefer not to get "taken" if I can help it. I have a 55g FW tank that is currently home to 4 apple snails. Soon, I will be adding 5 Xenopus froglets. (I will have 7 froglets but two of them will be in their own 20g tank). Anyway, as you are probably already aware, both the snails and the frogs. well..poop. A LOT. In the interest of maintaining a healthy environment where all life can thrive I've tried to incorporate many layers of filtration. Right now I have a Lustar IV Hydro Sponge filter in the tank, and an Aquaclear 70 HOB filter on it. My plan is to, once the tank is stable (it's still cycling), remove the Aquaclear, and just have the sponge filter running (I'll be stacking it, though, so I'll have an extra sponge in case I need a Q Tank at some point). I also have some plants coming that I will be adding to the tank. I will have driftwood planted with Anubias, and Limnobium spongia floating at the surface. I have a gravel vac and do the regular recommended weekly vacuuming and water changes. I was just wondering if a product like this would help me in keeping the water quality in check between weekly cleanings. I really hope this isn't addressed already, I used the search feature on your site and couldn't find anything. Also, I really would appreciate an opinion from the crew. Dr. Monks and Mr. Fenner have already been so helpful, and this site is such a wonderful source for impartial information. Thanks so much. Laura <Laura, by all means experiment with filtration methods. All that really matters is that you have a system offering upwards of 4 times the volume of the tank in turnover per hour. That's the key factor as far as nitrogenous wastes are concerned (ammonia, nitrite). Solid wastes are different. Solid waste (faeces, dead plant leaves, general debris) aren't toxic as such, and removal is more a question of maximising water flow through mechanical media. For that, the best approach is to use some type of canister filter; air-powered devices lack the "suck" to do the job adequately. Virtually everything else offered -- sludge removers, gravel cleaners, filter aids -- are pretty much snake-oil remedies for problems that wouldn't exist in tanks where adequate mechanical filtration was installed to begin with. In a tank with strong water current, all the solid waste will either go into the filter or else collect in one corner where the substrate is deliberately kept lower than the rest of the tank (usually at the front). During a water change, you just suck out this debris, and of course clean out the mechanical media in the filter every few weeks. Properly maintained, the gravel in an aquarium should honestly go years without needing cleaning, particularly if you install some Malayan livebearing snails to circulate the substrate and break down organic wastes. For what it's worth, in the tank where I keep a Panaque catfish -- a species that eats wood and produces sawdust as its waste product -- I have filters running at 8-10 times the volume of the tank in turnover per hour. Cheers, Neale.>

Re: Bacillus Bacteria filtration? Thanks so much for the tips, and I'll check into those snails and canister filter. Laura <Most welcome. Cheers, Neale.>

Re: Bacillus Bacteria filtration? Follow up questions..  9/27/08 So, I'm a little confused.. Should I use a canister in addition to the sponge filters in the 55g tank? <If you are concerned about solid wastes, then sure. But does all rather depend on how messy these frogs are. In a 55 gallon system I can't imagine half a dozen frogs will be a big deal really. Slope the substrate, and with luck detritus will collect at the bottom of the slope. Siphon out waste as required (or even use a turkey baster as a pipette.> (not very attractive in my tank) :-( .. But I know that the frogs are sensitive to turbulence, so I thought if sponge filters would do the work and minimize the turbulence, so much the better... BUT if a canister filter will do all that then... This is tough. <No, not really. Set the thing up with the frogs and the sponges. See how things go. If it doesn't work out, add a suitable canister.> On the one hand I want to create an environment that will make for happy, healthy, and thriving, plants and animals. On the other hand, there are budgetary and space considerations. And along those lines, a giant sponge filter in my tank definitely cuts down on the swim room available for my frogs. <Agreed; does depend on your aims. As stated, I'd go with the sponges or even an undergravel filter if budget is tight.> But a canister filter, definitely cuts down on the room in my budget. How are canister filters in terms of turbulence? <Depends on the size of the filter!> What do you think? Thanks. Laura <Cheers, Neale.>

Re: Bacillus Bacteria filtration? Follow up questions.. -- 09/27/08 Thanks for simplifying. <Happy to help.> One of the tads got an ARM today. <Ooh!> Too exciting! <In a Gary Larson sort of way, yes, I guess sprouting an arm would be... Cheers, Neale.>

BGK Problem... FW over and mis-stocking issues, no reading -08/25/08 We have a 55 gallon freshwater tank that has been set up for about three months. We have 3 discus, 4 swordtails, <Mmmm, "like" very different water conditions...> 4 clown loaches, 1 Pleco, 6 balloon belly tetras, 6 t-bone tetras, 1 elephant nose and 1 black ghost knife. <Not generally a good idea to mix weakly electrogenic fish species> The BGK and elephant nose were purchased together and were the first fish introduced. The BGK was about 3" when purchased and he is about 5" now. We added the other fish gradually. We do a 25% water change weekly. We are figuring out the feeding thing, and know we've been feeding too much, because of the water levels. Before we did the water change yesterday the levels were: PH 6.8, Ammonia 0.10, Nitrite 0.10, <These are toxic...> Nitrate .40. <Likely you've misplaced the decimal... forty ppm... is way too much> Last week when we took our water sample to the fish store, we were told the water levels were fine, except the ammonia was a little high. <Any ammonia is reason for immediate action. Debilitating to deadly poisonous> That, also, was before the water change. All of the fish have been doing well, except for swordtails, which were dying, one each day, for no apparent reason. <... do some reading... the "reason" is obvious.> It looked as though they were being picked on by other fish, because their fins looked very ragged. 8 have died. 4 remain, so we are done with swordtails for now (replaced them with the clown loaches). The BGK was doing fine until a few days ago, when I noticed that the white stripe on his head was pink. The next day it seemed even pinker, but he was still eating aggressively and chasing other fish if they came too close to his "house". Today I noticed that he has a worm-like thing hanging from his chin/throat underneath. It looks like a Tubifex worm. He isn't eating much, and is pretty much staying in his house when we feed them. However, his pink stripe is lighter, looks like it is turning back to normal color. We give the fish live Tubifex worms, frozen brine shrimp and frozen blood worms. Pretty much worms every day and alternate with the shrimp and blood worms. We sometimes give them flake food. Can you help diagnose the BGK or tell me how to help him? Thanks so much... Jere <All you need to know is archived on the WWM site... Your system is dangerously over-stocked... Start reading on WWM re Nitrogenous issues: http://wetwebmedia.com/FWSubWebIndex/fwmaintindex.htm the third tray down... Acting on this knowledge should save most of your livestock... Then read re each species/groups needs ("Systems")... Then we'll chat. Bob Fenner>

Re: BGK Problem  8/26/08 I guess you can tell I'm a novice, huh? After the water change, the ammonia was down to zero. <Ah, good> Today the BGK looks back to almost normal. The white stripe is a little off-color, but that weird worm-thing is gone and he has resumed eating. We haven't had any fishy deaths for almost two weeks, and the only ones that died were swordtails. <Mmm, you really need a much larger system... actually two...> I really appreciate your answer, and I plan to keep reading your Web site. I have been all over the Internet searching sites on aquariums and fish. I found so much conflicting information, that I was at my wits end. Then I found your site, which seemed much more consistent and extremely informative. I will continue my research in your archives. >Very good< The fish store where we bought the fish will buy back fish as long as they are healthy. We sold them four beautiful silver dollar fish when we bought the discus, because they told us the two didn't mix. The discus are still small, so we'll probably sell back more of our fish as they grow. I am in love with this hobby and my fish. I don't want to kill any more fish! Thanks again for your answer. I'm impressed with your expertise. <And I with your apparent even-mindedness. Cheers, BobF>

Maracyn Treated Tank 7/22/06 Hello... <Hi> I have added Maracyn to cure a supposed gill disease in my 29 g fw tank.  I pulled out the carbon, and noticed my water is getting foggy.  Is this common for this broad spectrum. antibiotic? Thanks!   Jenn Tony <The tank is getting cloudy because it is recycling.  Most likely the Maracyn nuked your biological filtration.  The cloudiness comes from the unprocessed biological materials and to some degree the recolonizing bacteria.> <Chris> Biological Filtration  - 2/21/2006 Please confirm I am correct here, for biological filtration I only need a piece of seasoned sponge ?. < No, a seasoned sponge filter like Hydrosponge.> Can this float on top, or do I need some weight to have it on the bottom of the tank? < The Hydrosponge filter is hooked up to an airstone and is already weighted in the bottom. Just hook it up to an airline and you are ready to go. Place it in an already established tank for a month and pull it out and place it in the QT tank when adding new fish.> This would suggest there is nothing else in the tank, except some PVC pipe and a sponge. < A sponge filter and a heater.> The reason I thought the internal filter was suitable is because it provides mechanical, biological filtration, and also good water movement for airflow. < By definition, any filter placed in an aquarium is an internal filter. It can be as simple as a sponge filter or as complicated an internal powerfilter. For QT tanks I think the simpler the better.> What is the difference between a outside power filter, please can you quote me a manufacturer and model #, and a canister filter? <An outside power filter would be like an Emperor that hangs on the back of the tank by Marineland. A canister would be like a Magnum 350 by Marineland. It goes under the tank and is connected to the aquarium through a couple of hoses.-Chuck> Regards Alan Dalgarno

Question about rinsing bio filter media with tap water 8/29/05 I have a question. I set up my 29 gal tank almost 4 weeks ago. I have 3 albino Corydoras and 3 blood fin tetras. All of them seem to be doing fine so far (have had them for about 2 and 3 weeks respectively). I did not know at the time, but I had what seemed as an excess of calcium, so besides doing a water change, I rinsed my bio filter under tap water (slightly) because it was all covered with this white stuff (that was all over the water, ornaments, etc). I read later not to do that because it kills the good bacteria. <Mmm, yes... at least not to do "so thoroughly", particularly in a newly set-up system> I asked somebody at Petco and they told me this bacteria should build back on. I want to know if this is true and how long it should take more or less. <Is so, a few weeks> I also have a carbon filter of course. I have had ammonia levels of 1.0 ppm pretty much since I set it up. <Dangerous> My nitrates were pretty low, almost zero since set up, as well as nitrites. I tested today (had not tested for about 5-6 days) and my ammonia is the same still, but my nitrites went up as well as nitrates, although nitrates are in the safe level still. I want to hear your insight about this, about the cycling of my FW tank, and so on. <Please read here: http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm and the linked files above> I feed my fish very little twice a day, but I am going to start feeding them just once do to the spike in nitrites as well now. Please let me know, I am not sure where and when to look for my answer. I had written an email a few weeks ago but can't seem to find the answer for it anywhere in the website. It was about RO water among other things. Thank you for your time.        - Zeke - <Read on my young friend. Your good, discerning mind will see you through. Bob Fenner> Powerless FW Tank in Australia 7/27/05 Hi from Australia. I'm sorry if my questions have been answer in previous submissions (I tried to use the search tool but couldn't find one that matched). I have a 60L (15 Gallon) tank that was going great guns until Monday when we had a power outage. I now have levels of Nitrite that are off the chart, I understand that my tank now has to be cycled but I don't know how to go about it with a tank full of fish.  I have 4 Bristlenose catfish and 7 Corydoras trilineatus. I am fairly new to keeping fish (I have only had fish for 8 weeks) but I have since learnt that while cycling I should do frequent water changes but leave the gravel alone as the good bacteria can live in the gravel.. Is this correct.? <The bacteria that break down the fish waste require oxygen. Many times after a power outage the oxygen level drops and fish/bacteria suffer. When power is returned it may take awhile to get the aquarium to recover.> and how often should I do the water changes? < Check the water for ammonia and nitrites. Both should be zero. If you are getting readings then you need to reduce the concentrations by diluting the water or by adding BIO-Spira from Marineland. Nitrates are less toxic and can go up to 25 ppm before a water change is required. But the tolerance to nitrates is dependant on the species.> After the power outage I have since done the following washed out the filter, done 2 20% water changes, removed the plants and when I do the water changes I add cycle (promotes bacteria) and Tetra Aqua Safe which removes Chlorine, Chloramine and heavy metals. Is there anything else I should be doing? < The plants absorb fish waste. keep them in the tank under good lighting to help reduce nitrates, etc...> Thank you very much in advance for your help :) Tash P.S I have since invested in a battery backup air pump. < You have become a smarter aquarist already.-Chuck>

NNR in freshwater? Hi Bob. <Hello Gustavo> I wonder if somebody already used the principle behind NNR in freshwater systems. I mean deep sand bed (1-2 mm size), good water flow etc. <Does work> The thing is I am reading and learning before setting my first freshwater system, planted with discus and a few other compatible fishes, but I own a reef system that really works very well with NNR plus heavy skimming. Do you have information about it? Thanks in advance Gustavo <Will, would take me some time to look up actual supporting data, but natural hypoxic/anaerobic nitrate reduction does indeed occur in such conditions in freshwater habitats. Bob Fenner>

Too Much Bio Filtration?? Hello crew, I have a freshwater setup 55 gallons. I have a Fluval 404 but I don't need or use carbon in the system (it is a planted tank). I'm wondering if there is such a thing as too much biological filtration? In other words if I fill the 4 trays with only biological media, will this have an adverse effect on the bacteria colonies. Will they out-compete themselves for ammonia/nitrates and meet their demise? Thanks <You can never have too much bio filtration. The size of each of your colonies will adjust up and down to your bio load. It's a great thing to have the amount of ammonia/nitrite be the limiting factor in their size. Four small colonies will adjust up very quickly should an ammonia spike happen. Don>  Cleaning Bio Media/Vacation Feeding Hi. I have some questions about cleaning the biological filter material. Am I supposed to wash the biomedia every once in a while? When should I replace the old media with new one?  I have two firemouths (1.5 inch) and a gibbiceps (2 inches). I am about to leave for 5 days and I can't get anybody to take care of my fish. I don't know how to get my fish fed during my absence.  If I use a feeder, much of the food would sink to the bottom, as the firemouths can consume only 1 pellet at a time. Moreover I would not be able to set the feeder up, so that a proper dose is distributed each time. It always happens that the pleco's pellets drop all at the beginning (and polluting the water) or clog the feeder's exit, leaving no food to pass through. In every way feeders have many serious drawbacks, according to my experience. Should I use those food tablets that last for a week and dissolve slowly in the water, or would it pollute the water a lot? Is it too much to leave the fish without any food at all? <You should never clean or replace the bio media. If this is a sponge that gets clogged, swish it around in some old tank water after a change. Never rinse under the tap. The chlorine will kill the bacteria. To replace or clean it would require you to recycle the tank. For a five day trip I would just feed them well for a day or two before hand and not worry about it. They will be hungry, but alive and healthy, when you get home. Don> Bouncing Bio Wheel Here I am resending this email. Oh and by the by, all my ammonia issues have finally resolved themselves! <Great. Probably the number one killer of fish. Bio filtration is very important> Greetings, and my deepest thanks for ANYTHING you can help me out with. Ok, so here's my issue, but first, I'm sure you will want to know all about my tanks, and such, (although that isn't terribly pertinent to my question). I have two ten gallons (I'm 16 and I baby-sit, so my income is hilarious, otherwise I'd have 55 gallon tanks or something) one of the tens is filtered with a penguin bio wheel mini, and the other, has two of these absolutely dirt cheap box filter thingy deals. And up until recently the cheapo filters had run for a year, with no fish killing problems.  One of the tens, houses about 10 or 15 Dalmatian lyre tail molly fry, which are almost a month old. And to be brutally honest, I have no idea why they are still alive, and apparently thriving. Crazy ammonia levels have forced me to perform water changes just about every other day, which I fear is only sending the ammonia/nitrate/nitrite cycle dealy even more out of whack. <Your work at water changes are why the fry are alive. Water changes will slow, but not stop, the establishment of the bacteria needed to cycle. I would suggest a simple change here. Replace the boxes with sponge filters. Since there is no floss to replace, bacteria will continue to thrive in the filter rather them be thrown away when you service the box. There is no real need for particle (floss) or chemical (charcoal) filtration if you do partial water changes as needed.> You'd think that would be my problem, but it isn't. Moving along to the OTHER tank, all of ITS issues started, when I started switching the filter's around in the different tanks. I moved the bio-wheel from the now-molly fry tank, to what I christened the Death Tank, so that the babies wouldn't all get sucked up into it. This of course, left the fry tank filter-less, so I put the two box filters in there.  Well, unfortunately, in the past week or so, I've switched them around again, because the fry are big enough to NOT get sucked up and I want them to have the nicer filter because they are oh-so endearing. Gosh, I'm really sorry to whoever is reading this, I realize it's long and confusing but please bear with me. So, here's where the question comes in: Because my death tank seems to have un-cycled itself (and by that I mean, the ammonia which had previously been flawless, is high, and who the heck knows what the nitrate and nitrite are even doing?!)... <You should be testing for nitrite and nitrate, not just ammonia. Very important>  ...fish have been succumbing to these stresses and developing illnesses. A week ago, one of my cherry barbs (which I've had for a year-ish) decided to get dropsy. He looked hilarious, but it ended sadly, when after treating with some Jungle Fungus stuff in conjunction with Jungle Parasite stuff. (I'd read it could be either, although I'm not sure my diagnosis was correct.) He died. Yesterday, I started treating my death tank for Ick. <Most bloating is caused by an internal bacterial infection. Fungus and parasite meds would be of little use. A medicated anti bacterial flake food may have been a better choice. Even a good wide spectrum antibiotic in the water may have been better. And why are you treating for Ich? First, you make no mention of white spots on the fish. Second, you already treated for parasites. Do not treat unless you need to>  Here's the part that I simply don't understand: For all of these medicine's I've been using to treat my cursed tank, they say to discontinue carbon filtration, which with my set-up, is all the mechanical filtration I've got. So what I've been doing, is putting the box filters into the fry tank, which has remained untreated, putting the bio-wheel filter into the death tank, which I first take the filter pad out of, because of course, it contains carbon. No wonder my tank is so screwed up!  Can the bio-wheel alone handle the filtration of 1 female Betta, two adult mollies, and two barbs? I sort of doubt it. <There are three types of filtration. Particle filtration simply removes any junk floating in the water. Any waste or old food that hits the bottom will usually stay there until removed with a gravel vac during water changes. This is less important than most people think. A good water change schedule removes far more junk than even the best filters. The second type of filtration is chemical. Usually done by adding charcoal. You only need chemical filtration if you are trying to remove a chemical, such as at the end of a med treatment. You can simply cut the black plastic cage on the filter insert and shake out most of the charcoal. The third, and by far the most important, is bio filtration. This is establishing a bacterial colony to convert the ammonia produced by the fish into nitrite, then finally nitrate. Most of the bacteria in your system lives on that bio wheel. It must be considered as if, and treated like, it was alive. In fact it is, with millions of lives working to keep your fish alive. When you start moving bio wheels around you may stress or kill the colony. Also, antibacterial meds will nuke the colony. That's what causes the ammonia to spike. Please read here on establishing FW cycling. http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm>  Could you possibly tell me how in the world I'm supposed to keep the tank clean, while medicating it? Any light you can shed on this would be greatly appreciated. <Stop all treatments and work towards re establishing your bio filtration. If you do treat you must do water changes to correct ammonia or nitrite spikes, replacing the med with each> Thank you so much again, I'm sorry this is so long. <No problem. Don>

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