Okay so about a week and a half ago now, I had a massive algae bloom in both my 5 gallon and my 10 gallon tanks. My 1 gallon hospital tank is fine. It bloomed about a week after doing a 75% water change in both tanks. I have no live plants, and no snails, etc. I'm going to look into snails, but what could have caused this? I took everything out, scrubbed tank, did a 100% water change, and scrubbed everything in very hot water. I don't have a testing kit so I don't know what the water levels are. It's not bothered my bettas at all though. I'm keeping an eye on both tanks now, but so far both are all clear. It was probably a week or so after I did the water change that I saw it. And it wasn't a gradual thing. It was maybe 2 days for it to turn my tanks fairly green. What's weird is in the 10 gallon, it was only on the side that had the light bulb (yeah I know algae needs light etc). Was just weird to see only half my tank green. I also had to take all the plants out, soak in hot water and scrub. That was fun. At least I know my lights would be good for plants now.