sponge filters - rate of flow

[bernie82]

Is there an optimum amount of water per hour we should be driving thru a sponge filter? Is 300 gph better than 50 gph? Obviously the size of the sponge is also a factor.

[Carol_Roberts]

That depends on water volume. 300 gph is too much for a 10 gallon tank and not enough for 150 gallon tank. What size tank are you talking about?

[bernie82]

Hi Carol. Thans for the help you gave me last week regarding a fish not eating.
Regarding this question, let's make the following asumptions:
two sixty gallon bare bottom tanks and each tank has exactly the same population of fish
Tank "A" is pulling water thru 7 inch x 3 inch sponge at a rate of 300 gph.
Tank "B" is pulling water at a rate of 100 gph thru the same size filter. Which is the better system?

[Carol_Roberts]

A is turning over the water 5 times an hour.
B is turning it over less than 2.

A is better for the 60 gallon tank. A turnover rate of 3 times an hour is a good figure. Filter's don't always perform at rating on box. Better to have a bit higher than too low.

[bernie82]

Hi Carol. I guess my communication skills are not good. I realize that the more water that passes thru a filter, the better it is.
I had heard that water should pass slowly thru a sponge filter for best biologiical filtration. I'm wondering if this is true. Is passing the water thru the sponge too quiclkly going to weaken the bacteria build up?

[Willie]

In this case, it makes no difference how fast the water moves through. The reactions occur one molecule at a time. As long as oxygen is not limiting, there's no such thing as a weak bacterial buildup. If oxygen is limiting, you would see it in the discus.

Willie

[Not2Day]

Willie
Contact time is a factor... though not necessarily a good one. Slow moving water through a dirty filter as opposed to fast water through a clean filter. Optmum contact time can be approached using mature filter material that is rinsed in tank water every day. IMHO it is best to remove your sponge filters daily for a good rinse. I am always amazed at just how dirty they can get in a day!
Dave