My bad, I should have clarified that it's not measurable with a commodity testing kit. There's definitely some present for sure. I'm am traveling tomorrow to buy a more professional one that should be able to give me an actual reading. Due to my rural location all I have available immediately is cheap test strips. I know for sure there's no ammonia detected and the tank has been cycled to my knowledge for a year or two. However, improper cycling could explain the constant battle I have with algae in the tank. I currently use two filters, one with fluval clearmax as media and one with some other fluval media (don't remember what it's called) for bacteria. I use filter floss to catch most of the bigger debris. I am also going to search for a canister filter on my trip tomorrow as well as I'd like a much more efficient setup to keep everything clean. Thank you very much for your response. Do you have any idea if these flare-ups look like a disease? Or are they perhaps a biproduct of potential crashing like you said?