PO4 and algae

[hwcheong]

Does it mean that if my tank grow lot green algae, PO4 test kit should detect PO4 in my water?

I use Azoo test kit but cannot detect PO4.

[lightningstrike]

not necessarily. there r other contributing factors as well. e.g. high nitrate, long photo period, etc. but i would recommend u to get a more reknown test kit like salifert to test ur PO4. a small trace of PO4 of 0.3ppm is enuff to do damage.