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FAQs on Freshwater Sponge Filtration

Related Articles: Freshwater Filtration, Know Your Filter Media, A Concise Guide to Your Options by Neale Monks, Power Filter Impressions,  A review of some popular mechanical filtration systems by Steven Pro, Setting up a Freshwater Aquarium, Tips for Beginners

Related FAQs:  Freshwater Filtration, Biological Filtration, Establishing CyclingFW Canister Filters, FW Hang-on Filters, Chemical Filtrants,


Sponge Filter and adding Fish Questions     11/17/14
I have a 28 gallon tank. The tank holds around 27 gallons. The filter is a sponge filter rated for 40 gallons. The ph is 8 and nitrates and ammonia at 0. This tank contains 2 guppy females, 5 neon tetras, 3 ghost shrimp, and
numerous bladder snails. Is the filter too strong?
<Nope. Manufacturers overstate the aquarium size rating for their filters.
They base them on optimal conditions such as clean filter media and understocking with small fish species. You can realistically cut the suggested aquarium size in half to get a real-world situation.>
Should I add anymore small fish?
<The old "inch per gallon" rule works pretty well for small fish such as Neons and Guppies.>
I was considering getting 3 platy fish,1 male and 2 females. Should I get them?
<Your tank should hold something like 20 fish in the 1.5 to 2 inch size bracket, so upping the number of Neons and getting a 2-4 female Platies shouldn't be a problem. I wouldn't add male Platies unless you absolutely
wanted to breed them. Otherwise, female Platies are just as colourful but don't pester other fish in the way male livebearers often do.>
Thank you.
<Most welcome. Neale.>
Re: Sponge Filter and adding Fish Questions      11/18/14

Thank you Neale!:)
<Always welcome.>

A few quick questions, DIY-ing some sponge filters, attaching these to powerheads, /GF  3/12/10
This is my first time ever e-mailing you. I have a few quick questions and I have been scouring the 'net and just cannot find them.
<Fire away.>
The deal is that I'm going to be DIY-ing some sponge filters for my 90 gal tank which will house goldfish. Seeing as I'll need an output of 900 GPH I'll be attaching these to powerheads.
<A turnover 10 times the volume of the tank is a lot, probably too much for fancy Goldfish. I'd aim for nearer 8 times the volume of the tank in turnover per hour. That said, it's easier and cheaper to reduce the flow through big powerheads than it is to upgrade smaller powerheads to larger ones if you find your filtration system isn't working sufficiently well.>
I'm hoping that the powerheads will be at the top (height of 18' for the tank) and I'll use a long tube to keep the sponge at the bottom. Still 900 GPH is a massive powerhead so I'm thinking of dividing it into 2 filters of 500 GPH or so apiece.
<Oh, I'd sooner go with four rather than two or one. Much better to spread out the water flow across the tank, rather than have strong flow in some parts and weaker flow elsewhere.>
Don't worry the questions are coming. In order for these to be effective I would need to know the surface area of the 10 PPI sponge that I plan on using as well as the average waste output of the goldfish. With a little mathematics I should be able to calculate the surface area but I cannot find anywhere about waste outputs on goldfish!
<Unknown. But for fish this size and shape, turnover rates 8-10 times per hour are adequate.>
I know they are one of the messiest fish available. I also know that the amount of waste varies due to everyone having different feeding regimens but I even then there should be a median somewhere or a chart even.
<It's a meaningless question. For example, a Goldfish fed flake will produce less solid waste than a Goldfish fed (as it should be) fresh green foods like Elodea and cooked peas. Simply a question of indigestible matter that goes in one end has to come out the other. Most anyone who's kept Goldfish in aquaria will tell you're they're messy fish, but that's more about the solid waste than the ammonia. In terms of ammonia, they're comparable to any other cyprinid of similar size, like a Tinfoil Barb. But Goldfish like to dig, and that means they "short circuit" undergravel filters, and this is one reason they're considered unusually messy, even though today relatively few people use undergravel filters.>
My other issue is that with such powerful pumps that I'll be using the water may not flow through the filter effectively.
Aside from bigger surface area on sponge and longer pipes I really can't figure out what else I can do.
<Water will travel through the line of least resistance. It's your job to make sure each powerhead is firmly attached to each sponge, so that the water flows evenly through that sponge.>
Is this going to turn into a project that I'm going to have to alter halfway through?
<Oh, it's certainly do-able. Whether it's cost effective is a whole other question. Any particular reason you're going against an off-the-shelf external canister, perhaps combined with a reverse-flow undergravel?>
I really am hoping to only buy one set of powerheads. Any help you can give me would be GREAT!
Thanks in advance!
<Cheers, Neale.> 

Sponge Filter Fan  8/29/06 I've read through your excellent page on sponge filters and have a few more questions.  It sounds to me like this is an excellent filtration setup.  Why is it not more commonly used? < Long time aquarists already know how good sponge filters are.> It appears to me to be simple, effective and inexpensive.  Is there a drawback?  Am I missing something? < Well, they look like crap in a display tank. Some Plecos eat them. You have to put your hand in the tank to remove and clean them. Bigger fish seem to disassemble them and knock them around. But for the most part they are a great filter to use under the right circumstances.-Chuck> Thanks so much for your excellent website!  If I do go forward with this system, I may be back with a pump question after a bit more research. Sponge Filter Ok. Now for my next question. What is a sponge filter? That is one thing about aquariums I am not familiar with.     Thanks so much again! Sarah <Well if that's the only thing you don't know about aquariums you know more than me! A sponge filter is just a piece of sponge with an air lift attached. You hook it up to an air pump and the bubbling draws the water through the sponge. They are used for bio filtration. Bacteria will colonize the sponge and control your water quality. It will take about a month to see the benefits. They do a great job of removing ammonia and nitrite after they are established. You never clean a sponge filter. If it clogs you just squeeze it out in old tank water. Never tap. The chlorine will kill the bacteria. They are not attractive, but if you get the flat style you can bury it in the gravel. I keep at least one in each of my tanks. They don't do well at particle filtration. I like to use them with a good power filter. But they can be used as the only filter if you keep up with your water changes. Don>

Air going to sponge (cycling) Hi Crew, My question is does it matter how much air is going to the sponge filter with cycling your tank? < Yes it does. The more airflow usually increases the water flow to so the filter becomes more efficient in cleaning the water.> Will high flow of air to the sponge remove more ammonia and nitrite, therefore decreasing the time it takes to cycle a tank or it does not matter? < It does not remove more but it does cause it to happen faster. The bacteria that break down the fish waste need oxygen to perform the process. More water flow means more oxygen in the water.> I like to keep the air at low speed because I have a Betta in my tank. < I am aware that Bettas come from slow moving to stagnant waters in the wild but I would increase the air to a medium flow and place lots of floating real or plastic plants in the tank to keep the surface water still and not disrupt the Betta too much.> Can you give me examples for each (advantages), when you would have a high, medium or low air to the sponge? Thanks, Mario D. < Measure you ammonia, nitrites and nitrates. If you tank is properly cycled then the ammonia and nitrites should be zero. When the nitrates are up to 25 ppm then you need to do a water change to bring them down. If you have any measurable ammonia or nitrites then increase the air flow to medium and check the levels again the next day. If the levels are down or changed then the bacteria became more active and were able to break down the waste faster.-Chuck>

Spare Sponge Dear WWM-ites, My wife came up with an interesting question this morning. In a spare sponge filter, kept active in case it's needed for a quarantine tank, how critical is the water flow for the bacterial colony? We have moved all our Swordtails and Endler's into a 20 gal tank dedicated to livebearing fishes. We have it set up fairly simply, with fake plants in the substrate and live Watersprite floaties for the babies to hide in (those that make it that far!) We've also moved the QT sponge filter to that tank, to get it out of the big community tank. My wife wants to cut down on the water movement in the potential-baby tank, and the sponge filter's big blurps of bubbles really stir things up. Since we don't need it for actual filtration (there's an Emperor 280 on the tank as well), can we unhook it from the air pump and still have it maintain a viable nitrate factory? As always, thanks for your help!  Glen <Yes, it will still retain enough bacteria to jump start a QT, but the bacterial colony will be smaller with less ammonia and O2 being pulled in. You would have a stronger bio filter ready to go if it was left running. Great plan to keep a spare sponge active. I wish fish stores gave out an established sponge with every new tank they sold. Don>

Question about a sponge filter / air pump / gravel Hi Crew, <Mario> Three weeks ago, I upgraded my setup to 5g with a heater and a sponge filter (Jr Dirt Magnet).  <Okay> My question is how do I know, if filter is functioning properly? The bubbles are coming out from the plastic tube where I inserted the airline tube. But can the bubbles be from the airline tube that is not properly connected or is it from the sponge filter?  <Not likely... if the air is coming out of the larger tube (the riser) all is likely fine> I am asking this because I do 20% water changes twice a week, but the water still seem to be a light brownish color. <Mmm, likely your system is just not "cycled" yet. Please read here:  http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm  and the Related FAQs  (in blue, above)> Is this harmful to the fish (Betta)? <Could be... if you have substantial ammonia, nitrite present> How can I direct any waste closer to the filter so that the filter to it pick up, if this makes any sense? <Does... best to use a length of small flexible tubing to once a week change out a gallon or two of water by vacuuming up this material (put the water on your plants) and replace with tap water that you've set aside the previous week> Also, I had to add a control valve to reduce the flow of air that is directed to the filter. Will this reduced flow reduce the life of the air pump (Rena 50)? <Good question... it can... if too much back pressure is applied... better to just "bleed" off the excess air... with a three way valve or a gang valve with more openings... that is, not put back pressure on the pump, but allow the excess pressure an outlet through another valve.> I did not include any gravel in my new setup. Should I or is it not important? <Mmm, can be an asset functionally and aesthetically... but can be left out... A good idea to have a bit... a sprig or two of "floating grass" for your fish... maintenance> I find without gravel, I have an easier time cleaning the waste at the bottom during my 20% cleaning. <Yes> Thanks, Mario <Welcome, Bob Fenner>

Fish Filter Issues, Pt. 2 Thanks so much for your help! The sponge is a great idea. <Not a problem!  Glad to help.> We have Daryl in hanging breeder tank in the regular tank. We added Maracyn. He ate supper and seems to be doing much better. <Nice chatting, Ryan>

Cycling a Sponge Filter Thanks Don, I appreciate your time and insight. I hate to drag on this issue of filters, but while shopping for a filter I came across a one piece with charcoal on top and foam on the bottom. Keep in mind I only have room for a 4 inches (height) and 2 inches (width) filter in my half gallon. My question is the charcoal/foam combination better than the all sponge filter? You said the sponge never needs to be replaced, but does the charcoal need to be replaced? Would you choose the sponge only or the charcoal/foam combination? If charcoal/foam, because it is one unit both must be replaced and how often would you recommend. One more question. Does the water and filter need to be cycled for a couple of days, before I can put the Bettas in the container. Or the next time I change the water I can introduce the filter, wait a few minutes and then add the Betta to the container? Thanks Again, Mario D. <I would go with just the sponge. Charcoal is only "active" for a short period. If you have to change the whole thing to replace the charcoal, you would loose the beneficial bacteria every time. You would never establish the bacterial colony needed for bio filtration. You only need a tiny sponge in this container. A little bigger than a silver dollar should do it. You could even trim down a larger one if that's all you can find. If the stand pipe is too tall, that can be trimmed also. It will take at least a month to establish the colony. Just add the filter whenever you get it and cut water changes back a little. Never more than 50%, but you want to do them more often at first. A test kit for ammonia, nitrite and nitrate would tell you when the filter is cycled and would clue you as to a healthy water change schedule once established. You can add the sponge at any time, but you will not get the benefits of bio filtration until that colony has darkened the filter. Should it clog up, rinse it in the water removed during a water change. I know it sounds strange, but it needs to be dirty and

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