I'd do everything everyone here has suggested. Get as much out manually. I'd remove the rocks, scrub them, rinse in saltwater, shake vigorously in saltwater to remove any detritus, then return them to the tank. Do all the rocks. Your bio load will be fine. Then gravel vac your sand and do a water change. No more than 30-40 percent of the water. Then add a new clean up crew, astrea snails, blue legs, emerald crabs. Not too many emeralds. Then do a black out on the tank. Turn the lights off for 5 days. Wrap the tank in something to block all the light. The corals may pale a bit but they will be fine. Feed the fish before the black out and once during and then after. Once algae takes hold, like you have, you need to take away one of its main food sources, light. While the light is out the phosphate removers and poly pads should remove any bad stuff in the water. Also you can use distilled just pick a better brand. As with most things the more it costs the better it's made. Pick a better brand. If you want to go r/o have a look at aqua fx. I just bought a 200 gpd for my service business and it works great. The price was great too. They have a website to choose from or their customer service people were super helpful to help me build exactly what I needed. Custom r/o at cheaper than regular prices. Once your black out period is done, remove the cover and do another water change pulling any algae that's left off the rocks as you go. Make it a small change maybe 5-10 percent. You should see that the algae that's left is dead or dying off. Hopefully at that point the clean up crew can take care of the rest. It will take time and you can repeat the whole thing again if you need to. If the corals look pale then give them a day or so with the regular lighting before you start again. Also if you have access to a par meter you might want to make sure you don't have too much light intensity going into the tank. We do this method anytime we take on a new client that's got your problem. It always works. It's going to take time to get your tank back but in this hobby patience is key. If you have any questions, feel free to write here or pm me, we're always happy to help. Good luck.