Cannot figure this out at ALL!!!!

[forsaken541]

OK my tank is a 90 gal over a year old with a 20 gal sump and a 5 gal fuge. My bio-load is not heavy, I run a urchin pro skimmer and have 6 maxi 1200 and a mag 9.5 sump return for flow along with my emporor 400 that i took the wheels out of and use for carbon and mech Filt. I started having a cyano problem about 4 months ago and here is what I have tried. Large water changes with RO water, new bulbs, I now only feed every other day, more PH's, switched from Oceanic to Ocean Pure salt, chemi-cleaned two doses with 30% water changes along with vacuming my sand more times that I can count.I also swittched my sand bed out about 3 months ago from play sand to aragonite. I am at my wits end and need some help. I love my tank but HATE this cyano. My nitrates are at zero so I'm not sure what to do. HELPPPPP!!!!!
Erik

 

[bradreef]

The phosphates are coming form somewhere. rock or sand are the two possibilities. The rock sounds like a possible choice. Try cooking it.

 

[forsaken541]

OK i just thought of something, My tank is in the basement and the sump is in a storage room behind the tank. My gas furnace is in this room as well and the sump sits near it. Could I be having CO2 probs from this furnace? and if so what could I do about it? I leave the door to this room closed most of the time as it houses our hot tub pump and filter setup so the noise can be a bit much with the door open. Could this be the mystery culprit?
Erik

 

[NaH2O]

I don't think I would look at CO2 unless you are having pH problems. Have you tested for phosphates? You can take a water sample from the rocks, and the sandbed to see if there are phosphates present there. Same with the nitrates - see if you get a reading from the rock. How often are you changing out your carbon? Also, test the premix water used in water changes for nitrates and phophates, also RO/DI.