Anyone know what I’m doing wrong to get this brown hair algae and why I have no nitrates? I have a low tech 5.5 gallon tank with 2 sponge filters and UNS Controsoil substrate planted with anacharis, pearl weed, and Anubias petite. I’ve have diatoms for the life of this tank (maybe a year?) I tested for silicates, and sure enough, my tap water has a little. So I tried pre-filtering water for water changes with phosguard, but I knew I couldn’t do that long-term, so I just put the HOB with phosguard right in the tank for a week. I didn’t leave it in because the HOB was too strong for my betta, but ever since I took it out, I’ve had this brown hair algae. I just tested my water after not changing the water for 10 days and the ammonia, nitrites, and nitrates were all at 0!? I retested the nitrates, carefully following the directions, and still 0. They’re usually at least 10 or 20 and I expected them to be on the high side since I’d put off the water change. So after the water change I added .5 ml thrive. I hadn’t been fertilizing to see if that made a difference. The old growth with the algae on it looks melty, but the new growth is green and algae free even without fertilizer. The light is on for 5 hours/day and the tank does get some sunlight when the blinds are open, maybe a couple hours/day. The tank went through a rescape/substrate change and subsequent minI cycle a few months ago.