Battling GHA since the beginning...

[Crocpete]

Hi, I have posted a few questions concerning nuisance algae and what to expect in a new tank (aka the uglies) but I am getting extremely frustrated. I have gotten some great advice, have read multiple posts and researched how and why algae grows and how to control it but I have had no luck. I have a 20g acrylic with a 2” live sand bed and about 15lbs of dry rock. I have a small HOB power filter, a small in tank skimmer & a 240 Koralia powerhead. The only inhabitants are a ocelarris clown & a tail spot blenny along with a serpent sea star & a small CUC of a few snails & hermits. Everyone is doing well, so I decided to add some corals. I bought a bunch of zoa frags on sale along with a chalice frag & GSP frag. These seem to be doing great also. I have had some issues with diatoms, cyano & GHA since the beginning. I have done multiple water changes, 10% weekly and 40-50% monthly. I have taken the rocks out and soaked them in a hydrogen peroxide mix along with scrubbing then with a toothbrush. I have siphoned up the sandbed and cleaned off the powerhead. I have started feeding every other day and lowered my white light ratio and length of daylight but the GHA keeps coming back. I beat the cyano but this green hair is killing me. It even seems like I have some diatoms coming back. I am looking for some advice that maybe I haven’t heard or read yet. I am hesitant to do any chemical treatments but I am leaning towards trying NOPOX because it is a biological fix. Any insight appreciated, thanks

 

[Crocpete]

Sorry, forgot to include parameters:
Ammonia- 0
Nitrates- 10-25ppm varies
Phospshate- 0
Alk- 9.3 dkh
SG- 1.025
Mag- 1020ppm
Calcium- 340ppm
Ph - 7.8
The tank is about 4 months old. I know the magnesium is low as well as the Ph and nitrates are a little high. I attached some pics as well

 

[Mical]

Up the magnesium to 1500 and your GHA will disappear in a week or two. I used Kents Tech M - was in the same boat as you, fairly new tank and Kents worked wonders.

 

[RJinPV]

I have GHA problems too and my Mg is 1500. Though I don't use Kent Tech M. The talk on the web is that it might be some impurities in the Kent Tech M that does the job (most say for bryopsos algae and not necessarily GHA) not the Mg levels. So if you try that route you need to use the Kent Tech M.

Your Nitrate levels are very high. My GHA experience is proportional to the nitrate levels. More nitrate, more GHA. I use NoPox and it does bring down nitrate levels. My tank is running less than 1 ppm consistently.