If you are introducing phosphates (from unpurified water) into your system, that will feed your HA. You said you were using a water purifier, but it probably isn't taking the phosphates out.
I'm not an expert, but another idea would be your bulbs. Some people report HA outbreaks when thier bulbs get old ~6-10 months and the spectrum shifts.
I would think about:
1.) Purigen or some other phosphate remover!!
2.) SKIM!
3.) Work toward a RO-DI unit, or get purified water from walmart (its RO-DI). At $.50 a gallon, its good for the short term, but bad for the long term.
4.) Think about a bulb change soon to very soon (might be a little premature in your case). Not sure about the coralife bulbs...maybe someone with experience can chime in??
5.) Careful not to overfeed.
6.) You can ramp the turbo snail population as long as there is food for them. They dont affect the bioload too much. Just make sure your HA is short enough for the turbos to eat it.
7.) Water changes can be helpful but remember that you're introducing phosphates with the new water (unless they have been removed via RO-DI).
reef-on!
EDIT: When you say slightly elevated on the ammonia...how much? This could indicate overfeeding and/or something just died. Unless you have macro or a good DSB, your elevated nitrates are just indicative of a needed waterchange. Sorry, i totally forgot to respond to your last post.
