Try this: Siphon a lot out, Turn the lights off, you can leave the timer going, but unplug the lights for 3 days ( full days) and don't feed the tank, preferably no ambient light either. Make sure skimmer is going. After words turn the lights back on and do about a 20% water change. Siphon out any remaining that you see, which there should be very little if any. This works with some, not many , but with some, it's nearly free and worth a shot.
I do recommend picking up a UV though. 75g would be a 15 watt UV. It makes a huge difference.
If the above doesn't work, try natural products for eliminating first before chemicals ( there are a few brands out there). Increased water flow on affected areas makes a difference for cyano and other algea's from settling.
Unfortunately Cyano, can grow easily on everything. Coral Magazine did a study a few months ago about it. So it may not necessarily be high Nitrates/Phosphates/Silicates although those are factors. It's a pain for sure , slow easy steps, if it's getting on coral's use a turkey baster to blow it off of them to keep them from getting smothered.
Go to petco and buy one of the small python's and just use the hose to siphon out chunks every now and then. Doing itty bitty water exchanges if the above advice doesn't work. Also, you can reduce your photo period to reduce the rate at which it grows. Corals as a whole need 5-6 hours for max photosynthesis. So you can reduce your time somewhat . Personally I don't run over a 9 hour photo period. To much algae production otherwise.
Chris
