Plant Filtration

[Rubes]

I have a small java fern and mini sword plant, both potted, and I was wondering how many gallons of water a plant filters. Both plants are about 5 inches tall.

 

[Jennewt]

I don't think there is any formula that tells you what volume of water a plant will filter. It really depends on the number/size of animals living in the tank. The only way to know would be to test the water for nitrate, and maybe also phosphate.