Looking for some input/help; my tank is suffering a big GHA & Cyano issue
 

I’ve been battling GHA since July 2014
I treated for Cyano last year
All was good until I messed with things …

I’d read about having balanced PO4 and NO3, and my NO3 was zero
Sometime back in Spring I tried to raise my NO3, as my corals were looking a bit lackluster. Note to self; don’t screw with the balance
Stupid me, I tried to raise my NO3 by feeding more. I know, you can’t raise NO3 by feedings … Lesson learned

I run Carbon and GFO
I change each monthly on a staggered schedule
Since this has happened, I've been changing the GFO weekly

The extra feedings didn’t go well. I’ve since had this ongoing issue with GHA, and it now turns out that what’s been killing all my snails is Cyano hiding in the algae
And on top of things I have to remove dead snails to stop the cycle (some poor buggers were brand new)

I’ve been changing my GFO weekly @ 150mls (instead of 225mls/month)
I’ve cut back the fishies daily pellets from 3 to 2 feedings for lunch, and just tonight cut it back again. They will only get one dose of pellets for now
They get one cube of frozen/night. It’s my mix that’s all rinsed and vitie blended.
I can’t cut the cube at night due to non-pellet eaters, but I may consider cutting a cube in half

My PO4 @ last test with my Hanna Digital was 0.02
With their variance, this could be either 0.06 or 0.008

I’ve been using PhosBuster Pro and haven’t seen a change yet with the GHA
I’ll continue to use it while I’m plucking what I can

Tonight, after 3 days of the PhosBuster stuff, I did a 15% WC
Normally I do 10%/week

I’ve been removing the GHA in clumps, big clumps, and I’ve had to regularly scrub some of my zoas as they are being overwhelmed by slime/algae

I don’t want to do a system reset at this point as my tank is finally starting to mature and some of my SPS are looking happy
It’s just past the 2-year mark

I've been thinking about changing my lighting schedule to reflect a MH unit
Instead of having my bulbs transition all day, I'm thinking about having a full-on light schedule during the afternoon to reflect a MH setup, and have my other T5s tuned lower to compensate for the difference

Any input is greatly appreciated

I had that once and probably a long shot but my carbon was laced with iron put a magnet on it to see if it sticks or 1 of your magnets in 1 of your impellers is broken

If your changing gfo weekly and your still getting po4 then that's an issue , dying snails will elevate that , what is No3?

You sure it's gha?

Is on your rocks or just the sandbed?

If it were me, I would just do a blackout and be done with it. If i recall you have been dealing with this for awhile now. Black it out for 3 days and your problem will be solved. Iv had incredible success with this. Good luck on the algae

I'd do some real water changes as well. Currently I'm doing 50% every 10 days and that's working well, nutrients getting lower all the time.

Yeah water changes in small amounts are a poor way to remove ongoing nutrients , the little you removed is back before the next change.

What's your debris removal like? If the funk ain't getting out then something is going to be more then happy to make use of it.
A heavy cuc count can trick a person into thinking they are doing good keeping things cleaned up and pruned, but if the junk they process isn't in turn being processed/removed, then they just create a nice little nutrient cycle for you. There great at what they do but only if we are following behind them ensuring what they process gets processed. If there just free to leave there nicely formed pellets of nutrients on the sand, in the rocks, any nook and cranny then they are working far more against you then for you. And at 2 year mark it sounds as though you may have been starting to stockpile nutrients, and now stocks are full and it's giving back.

I wouldn't even bother checking tank po4 levels for now. Just keep checking the output from your gfo and change when you see the output level rise. Gha is hard to battle with gfo alone. It can get access to available nutrients pretty quickly. The gfo picks up any that slipped past not the other way around. So staying ontop of manual removal is important. A blackout could work. Never tried but read lots of success stories. Do you have any macro? A simple ats could be employed for time being to give the gha a place to grow of you choosing and in addition allowing simpler removal. Non the less, if the exports are not on par with the inputs then it's a continual wall your up against. Re examining your debris removal methods and practices would be my first coarse of action. A cube of frozen is adding allot of additional nutrients you don't need right now. Cut it back to half, and maybe every other day?

im also battling pretty bad GHA. Gfo not rly helping all that much for me but i did notice them growing much slower when i manually remove them. About the 3 days blackout is it just turning off all the tank lights or do i have to cover my tank to make it totally dark?

100% darkness. I covered my display and my sump for 3 days. Worked like a charm.