How much do you put in your PO4 reactor

two things to keep in mind,

Algea also feeds off of nitrates so check those as well.

Your system could have po4 without it showing on a test kit. I ran into this same problem. The algea could be using up the po4's as soon as they're in the tank.

 

Well, PO4 is not the only reason for algae, just a contributor as are nitrates.

While my main tank is down, sitting in front of a window is all my live rock (100 lbs) is crammed into a 20g display with a 10g acting as a sump. Somewhere in there are 4 small fish, a few hermits, and a couple of snails. My PO4/Carbon reactor, skimmer, CDN are all crammed into the 10g... there may be 15g of total water... and I still have a light growth of algae on the live rock and glass.... it keeps the blenny with food.... and gives me something to do and both my NO3 & PO4 are "just delectable"... meaning I "think" I see a color shift off of white...

 

I have checked nitrates and they are near 0 also. But that is what i was thinking on the algea using up all the nitrates/PO4's before they are able to be detected. Do you think a PO4 reactor would help or would it be a waste of money?

 

I did see a decrease in the algae level when I put the PO4 reactor on-line... the "reactor" that I'm using came with the 120g tank that I got off of CL. I would not recommend any one of them that use a "twist to lock" lid. This one springs leaks (it is leaking right now) when ever the power cycles. If you choose to purchase one, get one with a thumb screw lid...

Did you check out the directions on SeaChem's site and read their test results? As for what makes up a PO4 reactor... could be as simple as placing the chemicals in a "filter sock" and placing into a high flow area... or using a standard 10 inch water filter with a refillable DI cartridge to hold the chemicals....

Yes, I would recommend running both a coil denitrator and PO4 "reactor"... on any size tank, combined with regular water changes, you'll have fewer problems over the long haul...