CUC recommendations?

[PeeperKeeper]

I know this is sort of an old tired subject, "How many crabs/snails per gallon....." but I did a search here and didn't see anything so thought I'd post the question. I should know this by now for as long as I've been doing this, but I wanted y'all's opinion.

I have a well established 75 gallon (over 10 years old) that I moved at the beginning of August. Before moving it was doing well except for a bubble algae problem. I've been steadily adding emerald crabs so that there should be at least 6 or 7 in there but I have a feeling some didn't survive the move so there may just be 2 or 3.

Just in the past week or two, I've noticed some hair algae getting started, and the rocks just generally look "dusty". I have a fuge but probably need to change the bulb on it to get more macro growth. Nothing ever shows up on n'ites nor n'ates but I haven't done a phosphates test in ages. I have no idea how many snails and crabs there are at this point. There may be as few as 4 or 5 of each. I haven't put any in since the move. So let's just say I'm starting from scratch. What would you add?

I know the way to control HA is to cut back on feeding and maybe do a few days of darkness then let the CUC take over. The fish inhabitants are: a big fat green Mandarin (who eats frozen. I've had him close to 2 years) a two spot hogfish, a mystery wrasse, a purple fire fish, a bar goby and two PJ cardinals. I've been feeding a frozen cube every other day so I'm going to cut back to just twice a week until the HA is gone.

[nemirn]

Long spine urchin... but after the HA is gone, he'll eat your coraline.

[PeeperKeeper]

I don't think it's bad enough to need a specialist urchin. I think I'm "nipping it in the bud" but I want to make sure I have adequate numbers of CUC.