I run GFO.
I use macroalgae (chaeto)
I test PO4 infrequently.
I have never had a PO4 reading.
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I run GFO (rowaphos) in a two little fishes phosban reactor (ever since day 1). I just change the GFO once a month. I have no idea if that is adequate (reason below).
I have had to mooch a bunch of chaeto from people (yourself included), because the first couple of balls of chaeto I got from someone never grew that well. Then got a few more balls of chaeto. Now my 'fuge is full of chaeto from like 8 different canreefers LOL!! I can not seem to get my chaeto to grow for the life of me
(that might be a good sign though.. i don't know).
I used to test P04 a lot (like the first month when the tank was set up), but I never ever got a reading from my test kit. The frequency of testing started to go down and is now sitting at nil. I have not tested for a long while.
The only algae complaint I had with my tank was the film algae on the glass that would appear more frequent than I would like. I recently discovered that this was mostly due to the low southern sun blasting into my living room in the afternoon when I wasn't home and hitting the tank dead on! I've fixed that by closing the blinds
(although my starfish aren't as happy with me now).
That's pretty much the sum of my P04 routine.