I've used it VERY affectively by directly dosing the tank with a small amount daily - but at the time I didn't have macro algae in the sump and no clam in the tank (as clams rely on the microalgae on their mantles to feed as they draw water through their mantle, you will kill them if you directly dose the tank with one in it - My mum killed hers by using a commercial algae treatment in the tank against my advise - 1 week and her clam as gone :-(
Anyway, here's my questions and suggestions:
- Can you remove the rocks to scrub and spray them with the H202? If so, great, this is the best approach. You only need to give them a light scrub with a brush, then spray them with the peroxide (if there is nothing else on the rock, don't be shy, I've used a 50/50 water and H202 mix before on my brothers tank) I let sit for 10 minutes and popped into a bucket of tank water to rinse off and back into the tank.
- If not, how low is the algae in the tank? If it's higher up, my advice is to drain the appropriate water out of the tank and spot treat the algae with a syringe (you don't need much at all) then top back up (perfect opportunity to do a partial water change)
- If the algae is too low and you can't remove any rocks, remove macro algae from sump and as long as you have no clams or Xenia, just treat the whole tank.
It's not a permanent algae solution, but if you begin to have a problem, it can help break down the algae for your clean up crew to manage. It oxidises the algae so fast and is very affective. I found my tank did really well when it required treatment and I do recommend it for people who are struggling with something that the CUC won't eat.
Be sure to take before and after photo's if you decide to go ahead.
MY DOSAGE & EXPERIENCE:
At the time I had a 40 Litre (10 Gallon tank) and the recommended dosage from the reading I did was 1-2ml per Gallon for other people using it (so, in my case, 10mls for the tank)
BEFORE:
I only dosed 2mls per day for 1 week for 40 Litre tank - Super low dose, but used daily
1 week after the treatment ended there was only about 5-10% of the algae left and another week later it was gone. My Coralline was not affected AT ALL and I could actually see it all, after the algae was gone.
AFTER:
I could not believe how much brighter the tank looked after the treatment. I actually think my corals were far happier in the 2 months after treatment than they'd ever been before, they thrived. The algae made everything appear more dull as it just sucked the light from everything.
Don't be afraid to use H202, just go slow. If I didn't have my clam (which I love and adore and am sad that it's growing too fast for my nano) I would periodically treat the tank (every 3 months, for a week at a time) to keep it looking sparkling clean. I had the most amazing clear glass for months after treatment.