Is my filtration good enough?

aus1230 · Nov 21, 2025

Started my 40 gallon in June and I’m currently struggling with phosphates for the last month or so. My phosphates have been as high as .61 as of 10/29 and I have gotten them to stay around .18 now. I was told by my local fish store that this will normally happen around the 6 month period and it’s to be expected. But I’m genuinely curious if that has passed and I’m still struggling to keep them low.
My current stock of fish in a 40 gallon is as follows:

Six line wrasse
Clown fish
Tail spot blenny
Two chromis
Blue damsel

I’m only running filter floss on both sides of the tank. Is this not enough? I have also placed GFO in my media basket and seen no positive results.

Mr. Mojo Rising · Nov 21, 2025

Did you start your tank with dry white rocks? Sometimes they can leach phosphate out of them, it took me 2 years once to drain the phosphate out with gfo. Phosphate remover like gfo or lanthenum is the only really effective way of reducing phosphates (except perhaps a refugium but IDK about that). Most filtration is aimed at nitrates.

Another way you can help is to reduce flake and pellet food (IDK if you feed it, just saying) and stick to frozen. And rinse the frozen out in rodi water, the liquid from the frozen food is very high in phosphates, so if you rinse it you eliminate the phosphates.

aus1230 · Nov 21, 2025

I started my tank with Carib sea.
So as far as washing the cube cut the piece that I want to put into the tank rinse it in a cup then pull it out before it thaws out. I’ll be honest I usually just put a cube in a cup with some RODI and let it thaw out then put it in the tank. And I only use frozen food.