@saullman apologies if this has already been covered:
I, too, am more concerned with your CUC not lasting than the algae, my hunch is if we can take care of one, that will take care of the other. If I were you, I might try siphoning that sand bed out of the tank, to be honest, its looking a little nasty. You can either replace it with new sand or go BB for a little while. Most of the nitrifying bacteria will be in your rocks so other than stirring up crap (which is a valid concern) not too much will happen. Siphon that ish out and do a water change.
- Have you done an ICP test of your water? (where you send it away to be tested)
- Any magnets/power heads in your tank that may be rusting?
- Have you checked for stray voltage? Could be coming from a pump, heater, etc (a cheap $10 multi-meter will tell you)
I, too, am more concerned with your CUC not lasting than the algae, my hunch is if we can take care of one, that will take care of the other. If I were you, I might try siphoning that sand bed out of the tank, to be honest, its looking a little nasty. You can either replace it with new sand or go BB for a little while. Most of the nitrifying bacteria will be in your rocks so other than stirring up crap (which is a valid concern) not too much will happen. Siphon that ish out and do a water change.