Nitrates are more accurate than that style po4. Maybe you could send water off for an ICP test? And .25 isn't crazy high. But it may not even be the right number. I truly think it's offYes, there is very little green algae growth but I thought that was because most algae fed off nitrates...I know that although .25 phos is high and can interfere with coral growth but do you think it will inhibit coralline growth if that number is correct? BTW, the nitrate test should definitely be accurate since I used two separate tests, one of which was Aquaforest Pro Test