i have 29 g tank, heavly planted, 10 cardinals, 2 oto, 1 fox, co2 pressurized, am using EI, WC twice week, the tank is 1.5 year old, 3.5w/g light.
over the last 2 weeks my po4 is high more than 2, i cant tell how high bc it goes over the lomette kit, my tap water po4 is 0 acording to water company and i confermed that with the kit? tank looks clean few algae here and there but nothin much. the fish are fed twice a day.
i stoped dosing po4 it went down to 1.5, no mater how many water changes i do still in the 1.5-2 range?
why its still high?should i continue holding the po4 ?
thanks

My guess would be rocks or other stuff in tank. The only other thing I can think of is if your using a buffering product some are phosphate based.

thanks for answering, but no new rocks, no buffring thing

Test your tap water with the same test kit. If it reads near zero then you can be more confident that the kit is giving valid numbers. (Assuming that the tap water really does have about zero phosphates, which is very unusual in itself. Most tap water gets phosphates added to keep the pH above 7 to avoid erosion problems with copper piping.)

If you don't heavily vacuum your gravel bed, it is easy for lots of waste products to build up there, including phosphates. Fish food has phosphates in it and so does fish waste.

vacuming the substrate is always been a dilemma, how do you do that if you have a heavly planted tank some time i do try but i end up missing the plants, i see pictures of tanks with carpet plant that you cant see the bottom, now those guys dont seem to do vacuming, some plant you wait for long time before the develop a good roots, do you really want to vacum near them?
am about to set 120g tank with AS, and it looks like it will be easy to pull the plants out just by looking at the size of the grain.
is there a trik to do this?
thanks

Vacuum just one section at a time.
Say 1/8 or a 1/4 th of the tank each week.

You do not need to do this more than once every year at most in most cases.
Some tanks you never do it.

Regards,
Tom Barr