[Kestrel]

My tank has been cycling for several months and when I started out I
used tap water. Then I bought a PO4 test kit and the result was sky high.
I got a RO/DI system and changed the water completely over a couple of
weeks. I have three damsels and some snails. I use Salifert Coral Grower
weekly to add trace elements. There is around 100 pounds of rock in the tank.

I got a Phosphate reactor and have used Warner Marine PhoSar HC to rid
the tank of PO4. My problem is this: I test the water one day and the PO4 is
undetectable. I shut off the reactor, wait a couple of days and test again and
the PO4 is elevated again. Can anyone offer any ideas as to what's going on?

Thanks for any input.

[pogodzib]

Your rock and/or sand bed probably has phosphate built up in it. If I were you, I'd either run the phosphate reactor full time and eventually it will pull all of the phosphate out of the system if you keep the media fresh, otherwise you can replace the sand bed and "cook" your LR.

[Kestrel]

Thanks for your input. I read somewhere that on occasion the Phos reactor
will pump the PO4 back into the tank and that's why I didn't run it full time.
The Warner Marine website says its good for a month.

I also read somewhere that the substrate...aragonite...i n my case, will
absorb the PO4 and has to be replaced. I hope it doesn't come to that.