Plants surrounding heater
Just posting this hoping it would help others... My six month old low-tech dirt tank (just lights and a heater) was doing great until about a month ago when I got some green water and a oily surface slick starting to develop. I hadn't changed anything in my routine or added anything to the tank. It took a few weeks to figure about what I think happened: My slowly developing jungle had engulfed the heater at the bottom rear of the tank and while the nearby plants were growing and *looked* fine, I think the heat was mildly cooking them and polluting the water with things the algae and bacteria love to eat. After some pruning and moving the heater clear things are improving nicely. So just a heads up -- because the plants touching your heater might not look damaged doesn't mean they aren't being stressed out.