I have the sponge filter shown here: http://www.fosterandsmithaquatics.com ... d_display.cfm?pcatid=3940

Can someone please tell me if the large bent tube at the top goes in the water or above the water? There are no instructions and the company I bought it from does not know.

I'd suppose it goes above the glass.

Thanks for your reply. Water does fall out of it, so it's either that it waterfalls back into the tank or actually blows right into the water. Some of their other filters have straight tubes which blow right in, so I'm just not sure.

Does anyone have experience with this and know for sure?

I could be wrong because I do not know about that particular sponge filter brand. Although I was under the impression that most sponge filters especially ones like that take in water where the sponge is (if that is the case) the sponge like other sponge filters goes inside the water.

I would also think that the sponge would need to be submerged under water to keep the biological bacteria colonized on it. I'm sure a stream into the water may keep the sponge with water but it would be passing mostly and spreading from inside out. Instead if submerged the bacteria would be passing from the outside in.

I personally think sponge filters are great because they seem easy to clean and last a long time. Simple and easy. Although the perks to having HOB filter like Hagan's AquaClear, although it may not be the best on the market. The idea of sticking extra DIY media to help out the balance of your water chemistry as well as do other things is a helpful thing. Although many apiarists know that all that is not necessarily needed and keep to simple while saving lots of money on not buying products like that. I guess it all depends what fits your needs best.

I have a few of these, and I keep them under the water level, but not by far. That way I don't have the waterfall effect and you still get lots of good circulation. They're quite adjustable too.

I have much the same filter running with the bent end of the tube a couple of inches below the water level in my Betta simplex tank. I suppose it might give even more water aeration if the water from the filter were allowed to exit near the water line and cause even more surface disturbance, but the fish are doing fine with it well submerged as it is in my tank.

while surfing the net I found one blog link. I think it might help you out - http://www.poolfilters.biz/blog/.

I fail to see any relationship there Manusmriti. We are talking about tiny aquarium filters that are run using air bubbles, not swimming pool filters.

The round sponge filters is the only kind i use. They are basically bio filters, you don't even really need the tube. Its purpose is to draw the water up and thru the sponge. You can bend it at the top, as my LFS does, or you can cut it in half with a saw like i do, or if it is well below the waterline, just leave it as it is. if it is above the waterline, it will have no suction and will only serve as a bio filter.