Underground Filter Q

[magicd]

Hey guys,

I have a underground filter which im using in a tank for breeding Zebra Danios. I have only put a few marbles over the filter. Is it better to use gravel and then put the marbles on top or is it fine how i have done it? (Please explain why) Also i do not have a air stone in my filter tube or anything in it. Do i need to have one?

Thanks

 

[DevUK]

I think you would probably need gravel in there. My knowledge of undergravel filters is limited, but from what I've read in the past, it works by pulling detritus down into the gravel, where the "good" bacteria that we rely on in this hobby builds up and does your bilogical filtration.

With just marbles in there, I'm not sure that process would work as effectively. Anyone else care to correct/agree/expand?

 

[shelaghfishface]

i had one with 4 stands and had an airstone in each, i dont understand how it would possibly without airstones,and i would also think it needs to be completly covered,as not to be would be defeating the object i mean an " undergravel filter " is exactly that,drags all the muck down underneath the plate,then the gravel (i think) holds it there, but if its not covered then i dont think its doing anything,well without the airstones, it isnt,

do you just have the base plate and a pipe standing up??

 

[smmetz]

UG filters are not very popular in these forums. People who know more about the history of the hobby than I do have posted that it is old tech, and was good before canister, hob, and trickle filters because widely available.

Anyway, UG filters work by using the surface area of the gravel as a home for the good bacteria. The solids that are drawn into the gravel stay there, and break down a bit hopefully. Marbles have much less surface area than gravel, so would not be nearly as affective at supporting the "biological" aspect of filtering. Gravel is better, because the smaller, irregular shapes have more surface area. If you go too small, like sand, it will not allow enough water flow to effectively filter. So, gravel is a good balance, if you are going to go with a UG filter.

UG filters are not all bad, but from what people here post, tanks with them should be totally stripped down and emptied about once per year. Vacuming the gravel only does so much, and they say this total tank breakdown is needed annually to get the muck from under the UG plates. If not, it will continue to decompose, and reduce water quality. Also, buildup around the UG plates can reduce water flow. Also, muck in the gravel can block many of the potential paths for the water through the gravel. This creates stagnant areas in the gravel where the good bacteria cannot thrive, reducing the "biological" filtering capacity over time.

Anyway, this is all just stuff I have read here, I have no first hand knowledge of UG filters.

 

[DevUK]

Also, to add, you need the air stone/line in the UG tube as the bubbling water moving up the tube cause suction, which is how the whole cycle works, sucking water into the gravel (and the dirt) and up the tube, back into the tank etc.

 

[rabbut]

Using UGF's to breed egg scatters isn't realy such a good idea IMO. The suction under the plate will pull any dirt onto the eggs increasing the risk of fungus on the unhatched eggs. Also, the eggs will find their way under the plate. They will then get pulled out again once they hatch by the current. Not too bad if you are driving the filter by air, but if you are using a powerhead (or pump) them the fry are mince meat (literaly )
I'd run an air powered box filter, and cover the bottom of the tank in marbles to a deapth of about 2 inches. Then the eggs are taken put of reach of the parents, and dirt is pulled away by the filter. Box filters are cheap, and can be built out of old food tubs. All you need is an air pump, which you may already have, some media (sponge) and some air line. Have a look in the hardware section of the board, for more info.

HTH
Rabbut