I have been battling GHA for some time now, and I cannot find the cause!
The tank is a 110 gal
XH with a 40 gal
sump. I do 20% WC
weekly and I was feeding every 3 days, I cube or a few shrimp pellets. The tank is not heavily stocked, with 1 Tomini Tang (about 3"), 6 Cardinals, 1 GSpotted Mandarin, 1 Perc Clown and 2 Cromis. 1 pep shrimp, 1 Skunk Cleaner and a number of hermits, turbos and Nassarius snails. I'm no longer feeding that often and they get food about every 4-5 days. Except for anyone who wants to eat the algae of course (happy tang). Corals include Sunset Monti, Galaxea, Pagoda Cup, mushrooms and Palys all doing very well. Hammer, Favia, Zoas, Horn and Trumpet are slowly dying. My Frogspawn was growing like mad, then after I went thru a major tank reorg, while trying to remove the algae, it rather quickly died.
Lights are a 4xT5HO with brand new Geissmann bulbs, but the whites are off right now. so the Actinic Plus are on 10 hrs a day. The skimmer is a SRO-2000 pulling out the cup of skimmate every 3 days or so. Cheato is growing very well (and pruned back every week during WC
) and I have PhosGuard in the reactor. A while ago I changed salt to Fluval Sea Pro, but that has caused a rather significant drop in my Alk
which I just noticed. I have it up to 7.0 from 6.5 ten days ago and am dosing Alk
buffer every other day to get it back up. I blame the salt for that as I am not heavily stocked on corals, and before the salt change I was running around 9-11dKH. After this bucket is gone, I'll switch back to AquaVitro or something else. Dosing until then, and more frequent checks too.
As for the rest of the numbers, here goes;
Temp - 79-81
Amm, Trites, Trates all 0 with 2 different test kits
pH - 8.3
Salnity - 1.0252 (digital probe)
Calc - 400 (up very slightly from my normal 360-380)
Phosphates - 0 (Hanna Checker, and liquid test)
Mag - 1500 (I have been raising it lately from 1300-1350 to try to kill algae)
Iodine and Silicates both at 0 as well, but I'm trying to dose Iodine up a bit)
The algae is mainly a GHA, but it is everywhere. Plus some Geledium, or Red Turf Algae.
So, any ideas as to where the nutrients are coming from, because I'm not putting very much into the tank and I'm pulling a fair amount of cheato out.
If I cant find the cause I'm afraid I'll have to pull most of my rocks out and put them in covered tubs and leave them for a few months to "cure" the algae out. I'm not looking forward to doing that.
edit: Water is RO
checked at 0TDS