I'd say 5-6 because of the severity. Make sure to give them plenty of shells (Around 10) so that they don't kill your snails.
Okay got it I really appreciate it!!
Exactly that. The GHA is fueled on both Nitrates and Phosphates, and I think the last time when you took the rock out, it killed the bacteria, causing a nutrient spike which is now feeding the algae. You can either dose phosphates or feed a bit more to raise them, but this will also increase food for the algae. Same concept of refugium, people use algae to "suck up" the nutrients in the tank. I would recommend using a product like Dr. Tims or Microbacter 7 to first replenish your beneficial bacteria, stay on top with removal of the GHA to prevent it from sucking up all your nutrients (depending on how much the hermit and urchin eat), and dose phosphates or feed a little more. The thing is is that here you'll have to really stay on top of algae removal or else the GHA will just be being fed more. I would recommend and urchin to go along with the hermits to really beat the algae down while being able to keep raised nutrients to prevent dinos. Good luck!
The algae won't go away based off of nutrients, it's more about the CUC. The nutrient levels are more about preventing dinos and maintaining stability, but an ideal range for phosphates is around 0.02-0.06, and for nitrates i'd say 5-10, your current nitrates are good.
Okay awesome time to get to work on this stuff
Wishing you best of luck
