GHA outbreak after Alk spike

[mmscuba]

Has anyone ever experienced this? I got overzealous attempting to restore the ionic balance of my reef using buffer, and accidentally spiked Alk off the charts. All of the corals retracted, and all inverts died (snails, shrimp, starfish). I immediately did a 50% water change, and over the next several days all of the corals are looking good and no fish died. What has happened is now my aquarium is becoming covered with GHA. I haven't fed the corals or fish since any of this happened, and all dead inverts were removed promptly, so I did not add any nutrients. The skimmer is producing its usual amount of skimate, around 1/2 gal per week. Here are my parameters as of this morning:
SG - 1.025
PH - 8.2
N03 - 8 ppm
P04 - .10ppm
CA - 420
MG - 1300
Alk - 12.8 DKH
I think the alk is down enough to add more snails now, I have begun dosing H202 @ 1ml per 10 gal, and I turned the white/red/green lights off, only running blues.
This is a 40B with 20 G Sump, softies and two small fish only.
Anyone else have any suggestions? I have never had a GHA outbreak like this.
Here's tha tank 4 weeks ago, not a single speck of algae, and it has been running about 3 years with zero issues.

 

[Retro Reefer]

Welcome to R2R! Be sure to say hello in the meet and greet section..

Considering you removed all the dead animals before they started decomposing the only thing I can think of that would trigger a GHA outbreak that quickly would be the quality of your make up water.. Im assuming your using 0 TDS RO/DI water? Making sure you are keeping up with carbon block replacement? anything change with your water source? (maybe obtain a water report from your local government) lots of nasty’s can get through your RO system and not register any TDS.

 

[mmscuba]

Welcome to R2R! Be sure to say hello in the meet and greet section..

Considering you removed all the dead animals before they started decomposing the only thing I can think of that would trigger a GHA outbreak that quickly would be the quality of your make up water.. Im assuming your using 0 TDS RO/DI water? Making sure you are keeping up with carbon block replacement? anything change with your water source? (maybe obtain a water report from your local government) lots of nasty’s can get through your RO system and not register any TDS.

Thanks for the welcome! Actually I've been a member of this forum for many years, I just haven't posted in a long time. I guess all my posts got erased somehow. But, to your point, I have a 4 stage RO system with double DI units, and my TDS is always zero. Good thinking though, because that is one of the first things I checked. Honestly, the only thing that changed before the outbreak was the KH. I hate to admit it, but I have been reef keeping for over 36 years, and this was the biggest mistake I've ever made. It was the holidays, lots going on, and I honestly got complacent and wasn't keeping a close eye on the parameters. It is also the first time I've had a terrible time with the ionic balance of a tank. Right now everything tests perfectly, so it does appear to be back in balance, but this dang algae!

 

[MixedFruitBasket]

Thanks for the welcome! Actually I've been a member of this forum for many years, I just haven't posted in a long time. I guess all my posts got erased somehow. But, to your point, I have a 4 stage RO system with double DI units, and my TDS is always zero. Good thinking though, because that is one of the first things I checked. Honestly, the only thing that changed before the outbreak was the KH. I hate to admit it, but I have been reef keeping for over 36 years, and this was the biggest mistake I've ever made. It was the holidays, lots going on, and I honestly got complacent and wasn't keeping a close eye on the parameters. It is also the first time I've had a terrible time with the ionic balance of a tank. Right now everything tests perfectly, so it does appear to be back in balance, but this dang algae!

Doabella Sea Hare is your friend. Greatest algae remover that ever evolved.

 

[mmscuba]

Doabella Sea Hare is your friend. Greatest algae remover that ever evolved.

Yes! Back home the pet stores would rent them out! If I could only find one here. Problem is once my tank was clean it would die.

 

[MixedFruitBasket]

Yes! Back home the pet stores would rent them out! If I could only find one here. Problem is once my tank was clean it would die.

Feed it nori. They do fine on that. Natural lifespan isn’t that long anyhow. They make for comedic relief in a tank. Especially when they fall off the glass in slow motion. And they are the slowest Ninja you will ever see—when you can see the.