argh, frustrating.

I've never tried algae before as one of my bettas, drapples reacted an allgeric...so am not sure how to help you.

are you using any bio-coats? stress 'chemical'? anything at all? those also could cause murky water quicker.. oh, how much food do you give neptune? what kind too? if you give him flakes (which's rare), no wonder. but if not, rule that out as long as you refreshen neptune's home every four days.

hope one of these will ring a bell and help you! good luck with your decision and I wish to see him, a beau picture soon!