[OL' SCHOOL]

I have used under gravel filters since the 60's and have never had problems with my tanks. This past year I have had to set up all my tanks fresh and have tried a little gravel in the bottom with a SPONGE FILTER. I am using a HYDRO II, which is rated for a 40 gl. tank ,in a 20 gl. and 15 gl. tank and they STAY NASTY! How do you use these things? I have tried them with and with out air stones but my tanks are still NASTY!!! Why does no one use under gravel filters anymore?

 

[gerald]

Not sure what "NASTY" means to you, but if you're referring to "biofilm" (slime) that's the mixed community of bacteria, archaea, and fungi that are keeping your fish alive. The same thing happens in an undergravel filter, but it's less visible. I like to put sponge filters inside a plastic container or jar (tall CD containers or Target peanut jars work well) and cover them with gravel and/or aragonite. That way the dirty water doesnt fall back into the tank when you lift the filter out, and you get some extra media surface area. I clean them in old tank water, not tap water.

 

[magicpenny75]

All my freshwater tanks (4) are filtered exclusively with Poret foam and they are all sparkling clean. I take the sponge out once every three months and smush the solids out in a bucket of tank water.
What is the flow rate through the sponges? Maybe the problem is exposure rather than media. All of mine are in hang on filters except a 6" cube in my 50 gallon tank which is drawn through an old AC50 power head.

 

[OL' SCHOOL]

NASTY = Cloudy water with a white to yellow brown tinge. Bottom of tank seams stagnant. These filters are air stone driven so I have no idea what the flow rate is. I have tried them with an air stone and with out. ( Have seen them used both ways in clips from YOU TUBE ) Air valve is turned on max and is powered by a very good air pump. They show obvious water movement at the surface of the water but not much else. I have at least 6 small cory cats in each tank plus the fish I am working with (Angels and Rams). All fish are Healthy and active. I have 1 potted plant in each tank (Cera var.) Change 1/4 water every other week with treated heated water. I have added outside filters, WHISPER 40'S, to help clean up the sediment but water is still cloudy. As Gerald said, the same thing happens with a undergravel filter , "but it's less visible". To me, that's the whole point.

 

[OL' SCHOOL]

bump

 

[monstermanhbf]

I'm having the same issue and have a single outside filter I noticed that if I move a rock or gravel a lot of crap get stirred up I'm thinking an under gravel filter might be needed

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[SantaMonica]

White cloudiness is usually a bacteria build up from excess nitrate or phosphate. It can grow faster than the foam can filter it out. But as the source of nutrients (usually something dying) goes away, the cloudiness goes away too which is why Ol School probably did not reply again.

Even with no filter at all anywhere, if you don't stir the gravel up, the water will eventually become a natural lake and form biofilms on the surfaces which clear up most of the particles, although it won't be unnaturally crystal clear like with foam/floss filters.