Sizing Sponge Filters....

[Soulman15]

I have a question.  I was just was given 2 - 40g breeders that i plan on using sponge filters on. 

As you probably know, FX6s say they they can filter 400g and have a 925 GPH rating.  We also know, that rating is not accurate because they are based on no media in the filter and no head pressure.  I have always been told to cut the 925 GPH in half, and that closer to their real output.  

Which leads me to my question....

Should you upsize a sponge filter in the same manner?  Is a sponge rated for up to 40 gallons sufficient, or should i go up to one good for 75 gallon?

Not sure what i plan on doing with the second 40 gallon, but i am starting off with 2-3 baby EBJD and growing them out in this 40 gallon, so the bio load will be small at first, but will grow.  EBJDs get hardier as they grow and i plan on keeping them in there until 5-6 inches.

[Brandy]

Congrats on the tank score!! I love my 40 breeder.

Sponge filters are mostly biological filters. A 40g (large on ACO) sponge filter will be sufficient to keep your fish healthy. I have 2 in my 40 breeder because I like more even flow in my tank--no (or fewer) dead spots. That isn't about filtration. That is about having enough current for the footprint and amount of decor in my tank. 

Mulm will build up with a sponge filter. You can take that out by vacuuming. I don't mind this as it is less important than vacuuming your house--health wise. So I do it when the stuff on the substrate bugs me, not because it is a problem for the fish who enjoy rooting around in it. By putting one filter in each corner I mostly collect the mulm in those places, and it is hidden behind plants...which also like the mulm.

Most of what a sponge filter does is different than what a canister does by leaps and bounds. You wont have the water polishing capability. That bothers some people. But they are some of the easiest filters ever, so I love them.