I’ve never had an outbreak of
Cyanobacteria. That is until now. It basically covered my entire scape. A thick poisonous layer on rocks and plants. It was so bad I had to waft it off every few days and siphoned it out.
Unbelievably, the plants were doing well despite this. I know the O2 levels were good. I had a lot of surface movement from the lily outflow, and an Eheim skimmer on constantly.
Nutrient levels were lower than I normally use. Been lean dosing.
There are 3 factors I think may have triggered it. 1. We’re in the middle of a heatwave. 2. Too much deadwood releasing organics. 3. And perhaps most important, light intensity was way too high.
I’ve been using an
ADA Solar Plus for the first time. Must admit colour rendition is awesome but, it’s not controllable and the light spill is horrendous even with the shades on. Especially since it needs hanging a mile above the tank.
So what did I do to fix it? 1. I swapped the light out for my dependable and controllable Twinstar 600s. 2. Then I removed all the DW. 3. Reduced the height of the rock stack to get better flow around the tank. It’d become unstable anyway , so had no choice. I didn't want it falling over and smashing the tank. TBH it was originally designed as an Iwagumi anyway and I'm much happier with it that way.
That made things perceptively better. However, the cyanobacteria persisted. In the end I got fed up and dosed the tank with 600mg of Doxycycline. I know it's frowned upon ethically but my fish also had finrot. Just in case you're wondering they came that way from the LFS. Never buy fish without your glasses.
Anyway, it worked. The cyano cleared up in a couple of days. That was a couple of weeks back now and it hasn't come back. I guess the key is to remove whatever may have been causing it in the first place.
I wasn't concerned about crashing the tank or the filter. A lot of the heavy lifting isn't actually done by bacteria, it's done by archaea. Doxycycline doesn't affect them. Also, as we all know the plants do a lot of heavy lifting too.
The pic below is how it looks now. I trimmed the tenellus at the front so it's not looking its best atm. And excuse the dirty lilies, I haven't had time to clean them yet. And it's still very much growing in.
