I was having a lot of issues with red cyano on rockwork and the sand.
After doing all the usual things including improving flow, blowing off the rocks, and checking nutrient levels, it was still coming back and I could never quite catch what made some days worse than others.
There is a lot of info about cyano online, but a lot of it is repetitive and possibly wrong (like blaming an excess of phosphates and nitrates even though cyano can be a problem in ultra-low nutrient tanks also).
Bacterial Imbalance
One article I read explained that cyano takes hold when there is an imbalance of bacteria and that by dosing good bacteria you can help beat back the cyanobacteria.
So that led me down a long path. It’s not easy getting reefing supplies here in Finland, especially not living things like bacteria (in winter especially), so I decided to work with what I had and figure out why my tank didn’t have balanced bacteria and what I could do to help the good guys along.
Water Parameter Testing
My nitrates were testing low but phosphates still looked high. I sent an ICP test to Triton and the results were mainly alright apart from nitrates and phosphates almost at 0.
The testing kit I had for phosphates had colored over time and was giving the wrong result. I bought some Hanna checkers and have been keeping better track of those numbers now.
Why No Nutrients?
It could have been algae using up all the nutrients, but I didn’t see any particularly bad algae. Bit of green hair in the sump and my Caulerpa macroalgae in the refugium.
I do have a lot of Asterina so I considered whether they were keeping all the algae down but then I realized it wasn’t important to find out what was removing the nutrients. It was more important to get nutrients into the tank.
if the checkers read 0 nitrates and phosphates, the coral (and presumably good bacteria) don’t have anything to eat so time would reveal what was going on but first I needed nitrates and phosphate.
Raising Nitrates
First off I was liberal with feeding, but it didn’t make a difference. I don’t have a huge bioload from fish and critters so I could never feed enough.
Removing the Skimmer 10.2.2024
So I decided to try something new and took my skimmer out. Bear in mind that my system is mature. I have filter socks that are changed weekly, I have a pretty big refugium on 24/7, I do water changes bi-weekly (not very big ones though) and I also have a giant clam which is a cleaning factory all by itself. So life without a skimmer might not be so bad as long as I keep track of my parameters.
Will keep this post updated with the results of this experiment and what happens with the cyano. I check levels every week so I can always put the skimmer back if things go south.
My tank is so much quieter without it though… And it would give me a spare area in my sump so fingers crossed.
Updates
22.2.2024
It’s been 2,5 weeks since I took out the skimmer. So far results are promising. The first thing I noticed was much less algae on the glass. I always had a dusting every morning and usually again by evening but now it’s noticeably less.
The red cyano has buggered off from the most pervasive places including the sand bed. It’s not fully gone yet but it is 50% better. Phosphates are reading 0.03. Nitrates high tester are still 0.
Coral growth seems to be gaining momentum with my wee bird nest stick encrusting faster and all my other coral looking good. My rose BTA’s are the only things that don’t look so good. My green BTA:s are doing fine though and the Haddoni, so I am thinking it is a feeding issue rather than nutrients.
3.3.2024
I finally had a reading for nitrates today (phosphates are still low). Discosoma and Zoanthids are all looking much bigger and fluffier. I am not seeing any adverse effects yet on any of the rest of my coral.
My glass isn’t nearly as bad as before, it can go a few days without cleaning which has never happened before. When the skimmer was in, I’d get quite a thick layer of orange algae (diatoms I presume) on the glass and have to clean it off at least once a day.
The red cyano is now 90% gone. There’s still a bit in the centre of the tank with the lowest flow but it has been getting smaller and smaller.
I was a bit worried about oxygen with the lack of skimmer, but my powerheads are agitating the surface a reasonable amount and I haven’t seen any oxygen issues so far.
My skimmer used to pull out a fair amount of crud, I don’t really like the idea of that crud staying in my system but I also have so much microfauna in there including Asterina, baby snails, copepods, and unidentified weirdos, that I hope they can clean up the detritus that the skimmer used to take out. Time will tell.