I'm keeping a small 20 gallon cube. I have 3 clownfish with 1 damsel. I feed mysis once per day and recently switched to home-brew food. I never experienced any problem until I noticed all of the SPS suffering from poor PE and STN on most of them. Not to mention they are all dark brown without any growth at all.
I don't usually test PO4 but I tested today and shocked how high the reading is. I'm using Red Sea Pro PO4 kit and had to use high range method to got results in between 3ppm-5ppm! NO3 reads 0.5ppm on Salifert.
My nutrition control is vinegar dosing via dosing pump. Tank is BB and established 10 month ago with all dry rocks. I change water weekly for about 3 gallon with Salinity salt. I run a skimmer that rated for 65-70 gallon 24/7. I do not use GAC/GFO.
Since PO4 is the problem so I mixed 40ml of Rowaphos and 15ml Phosguard into media bag placed in sump, also added 100ml Seachem GAC. But I personally don't want to have to rely on these absorbers long term. I'm suspecting the source of PO4 is from my home-brew food, so I will stop that as well.
I'm wondering what I should do to maintain low PO4 level? I'm thinking RDSB, small refugium with some marco algae, maybe a few mangroves; or just stick to carbon dosing (I have bio pellets reactor too)? Will my Acro to recover once PO4 level is low again?
ALK: 10.5-11 dkH
Mag: 1250-1300 ppm
NO3: 0.5 ppm
PO4: 3-5 ppm í ½í¸±
Any input appreciated!
* I'm also concerned if rock will absorb PO4 and create a long term problem. Should I better just start all over again?