Yeah that’s what I think is happening. It grows and the more it grows, somehow there isn’t enough nutrients to feed it and starts to die off. Then eventually it starts up again. Yeah I would say bioload has been low with just snails, hermit, two clowns and a yellow coris. But I was doing water changes a week with 5 gallons and I think that isn’t necessary at all! Hence I’m going to cut back to maybe a total of 5 gallons a month.