Question about filtration


New Member
Dec 9, 2021
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Raleigh, NC
Hey all, I have a question regarding filtration for my 20gal high tank... I'm using this sponge filter rated for up to 20gal powered by this Tetra Whisper air pump rated for 20-40 gallons. I chose sponge because I'm using a sand substrate, and I wanted to protect shrimp babies. The tank has live plants.

My tank is stocked with 2 honey gourami, 1 nerite snail, 4 neon tetras (I originally had 11, but got a bad batch), and 6 cherry shrimp (some are berried). AqAdvisor rates me at 153% filtration right now, but I want to add habrosus corydora and some more tetras in the future and I'm learning I'm supposed to have way more filtration than what's rated for 20gals?

How do I make sure the filtration is adequate? AqAdvisor rates filtration capacity at 79% with my stock plan. Can I just split the airline tube with a valve and add another 20gal sponge? Or should I add an HOB filter instead -- and what would work best with sand substrate? :/ (concerned about sand wrecking the impeller)
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Fish Crazy
Jan 13, 2022
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I've got a 29g tank with a hob rated at 20 to 40. Initially set it up with gravel, but changed to sand to accommodate my corys at @Byron suggestion. Best decision ever.
So, my humble suggestion would be to go for a hob, and use a piece of sponge or biofoam to cover the inlet and avoid any issues with the sand and the impeller, and that way you'll be all set for any future additions to your tank too. Just my 2 cents, Other members might have other suggestions,


Fish Guru
Tank of the Month!
Feb 25, 2009
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This issue comes up a lot on TFF...having "enough" filtration, and it is usually accompanied by the mistaken view that "more" is better. Nothing could be further from the factual truth.

The filter has two different aspects. One is actual filtration, the other is water current. The latter is or can be very significant for fish, which is why some of us always ask about the intended fish species. Forest fish do not need to be battling currents, and remember, in the aquarium the filter is always running so these currents are impacting the fish 24/7. Some fish need these, but others do not. The fish mentioned in post #1 disqualifies HOB because in a standard 20g tank one of these will create far too much water current, and the fish will not be able to escape it to rest. A single or dual sponge filter is best for the fish named. The linked sponge is fine, though you might want to consider another type, which will still be connected to the air pump you have, and that is the dual sponge pictured below. I have one of these in my 20g and 29g tanks, and the latter has pygmy cories, green neons, ember tetra, pencilfish. And floating plants. The advantage of this sponge filter is that it can be positioned at any vertical height, it is not on the substrate, and the two sponges are adjustable to any horizontal angle.

This brings me to the filtration aspect of the filter. Mechanical is the only filtration you really need to bother over, and sponges are just about the best for this. The sponge is also an excellent host for the bacteria, so you have biological filtration. Not really necessary in a planted tank, but it will occur no matter what you do, so accept it and don't over-encourage it.


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