Any experts out there on dealing with Cyanobacteria

[Branch]

Hi, I'm struggling with keeping cyno down and although I researched extensively about the subject I can't resolve it. To be honest in 30 years of keeping discus this is the worst I've ever come across and I'm struggling for answers.

The tank is 150 gallons, planted with C02 and has been running for 22 years. It has daily water changes (RO) of 20%, heated and matured overnight and N03 and P04 are <20ppm and respectively so it's not a case of excess waste/nutrients. Lighting is LED and on 9 hours a day, staggered re wake up and wind down. PH is 6.5 and temp 28/9C.

I tried a product 'Easy Life Blue Exit' to (purportedly) remove the cyno and besides being ineffective I believe that it killed the clown loaches I had as a day after dosing the tank they started to go crazy and within 48 hours were dead, no other fish, including the discus, were affected. I suspect that it may have caused issues with the bacteria in the tank that may have lead to an ammonia spike but I cannot say for sure plus the discus were totally fine.

I have tried blackouts and reduced the duration of the lighting but to no real effect.

Any help would be greatly appreciated as I believe experience trumps books.

[bluelagoon]

I've gotten rid of it with 3 to 4 day total black out. During those black out days it is very important that no light at all gets in the tank. Plants should be able to handle a few days without light. Another easy way is if you don't mind using antibiotics you could dose with erythomycin. And you need to lower your phosphates.

[Willie]

Blue green algae, a form of cyanobacteria, is distinctly different from other algae which are higher plants. Not only can cyanobacteria photosynthesize, it can also fix nitrogen. So it can proliferate even when nitrate levels are low.

Mervyn's comments are on the right track. Reduce your light period. You can't totally darken the tank because it's planted, but you can keep the lights to maybe 4 hours a day. Increasing water changes will help, but not rid you of the problem because the bacteria can produce its own nitrogen. But the water changes will reduce phosphate, which is the limiting factor. I suggest you do a couple of consecutive big water changes (75% - 80%) to get the phosphate level down. Then look at what could be a phosphate source in your tank - perhaps limestone rocks.

The only way to 'kill' cyanobacteria is a wide spectrum antibiotic, which will also wipe out your cycle. That's really not a good idea. Most of the algacides in the market will handle other forms of algae but not blue greens.

[jwcarlson]

Doesn't a UV sterilizer kill it?

[Willie]

UV sterilizers actually do not kill anything. The rays cause dimers to form along the DNA strand which blocks further replication, so the cells do not divide. However, the cells are not killed. In this case, they will continue to photosynthesize and fix nitrogen.

The issue is that high phosphate in the water is leading to a blue green algae bloom. Unless that's addressed, the problem will just recur.

[captainandy]

UV light will kill free floating cyanobacteria. In addition, just google or search amazon for a variety of chemicals that will assist in removing it

[Branch]

Thank you for all your comments. Addressing them one by one please see below;

1. All blackouts I've tried have eliminated the cyno for a short period but it returns within a week or so starting with patches on the gravel and then it cover the plants and bogwood.
2. Erythomycin destroys the tank cycle and I don't think it's worth the risk.
3. Problem with such massive water changes is storing the water before hand at the right temperature, a shock in temp changes can stress the discuss I've seen them develop white spot from the after effects of large water changes and related temp drop.
4. I've used UV in my marine tanks but never freshwater.

I think the big take-away here is phosphates, getting this down but I struggle because of the feeding regime I still incorporate for my young discus. Perhaps some form of absorption media will help? Nitrate isn't a problem, in fact cyno appears to thrive in low Nitrate environments.

[captainandy]

Phosphates are not the single problem.
I’ve had extremely low phosphates and nitrates in marine SPS tanks and still had outbreaks of
Cyano. Use some of the cleansers as listed on most fish on line stores

Blackouts do nothing, short and long term.

You don’t need to make a
Mountain out of a mole hill

[bluelagoon]

The blackout worked for me along with larger water changes a few times. It starves the algae of light in the bacteria long enough to kill it and is the safest alternative for fish and the environment. You can't get antibiotics legally here where I live and blackouts will work if you fix the problem. Something is out of balance. Could be phosphates or could even be more light like the summer months when the spores are airborne. Seems this is the time of year it generally shows up in my tanks if it does. The plants will live a few days without light: at least mine weren't affected by the darkness. Total darkness seems to work better rather than taking a peep to see how things are going. Don't let any light in the tank; the fish will be ok a few days without food. I see you use CO2. Do you use nutrients and is your tank heavily stocked with thriving lush plants? Is it possible you can show us a pic of the whole tank?

[bluelagoon]

Reading your 1st comment on. "not a case of excess nutrients". But you've only changed small amount of water in the tank over the many years and in time lends to old tank syndrome. Google "old tank syndrome". Leaving 80% dirty water behind every time. I think you need to find a way to age more water.

[Branch]

Thanks for the further feedback.

PO4 0.03mg/l and N03 20 mg/l today. Have reduced lighting by 2 hours a day but gravel substrate was like a green carpet.

As I said, I tried cyanobacteria removal products and they did little to solve the problem and I'm certain the Easy Life Blue Exit killed my Clown Loaches so I'm averse about putting any products in to the tank.

I could try another blackout but the discus I have are only 6 weeks old and are fed three to four times a day, and even then they're jumping out the tank to get more food. To starve them at such a critical grow out phase would impact on their size and the last thing I like to see is stunted fish.

I doubt it's old tank syndrome as 20% - 25% a day of pure RO has never been an issue for me and although I can take it up to a third a day I doubt it would eliminate the algae.

Here's a video, albeit it's after I've cleaned the gravel and bogwood plus there are fewer fish in this tank now as many were transferred.


https://photos.app.goo.gl/nTMmsSNrCS6yjNUh6

[bluelagoon]

Hope you don't mind but I see no reason to use CO2 for the plants that I see in the video. They are all slow growing plants and won't take up much nutrients and will get by with about 8 hours decent of light. That is a lot of fish for young discus to compete with and grow well. What goes in the tank needs to come back out, so I would increase the WC's. Why are you using RO water? I have gotten rid of cyano easy with black outs and large WC's over the years and is safe.

[Branch]

I've gone without C02 before and these plants barely grow whereas with it new leaves on the Anubias appear almost weekly plus they, albeit before the onset of cyanobacteria, look much better and healthier. I have always kept a strict eye on the competition and believe me the discus get in first and devour the beefheart whilst the community fish mainly eat the flake food and a share of the bloodworm that the discus don't want.

As for RO water, our tap water here is very high in nitrates due to the farming and RO has always been my go to water. I'm not short of RO water I'm just only able to heat 25 gallons at any one time, the capture butt is nowhere near any electrical supply so it has to be transferred to the maturing butt.

[bluelagoon]

Cyano uses CO2 to make oxygen. The more CO2 the better cyano grows. I think the reason for so many breakouts of cyano in the lakes in recent years is due to increased heat and CO2 in the air.

[Branch]

That's interesting, thing is I went without C02 for a year and had terrible Cyano but I will do some research. Have upped my water changes to 40%-50% daily and reduced the lighting to 7/8 hours a day. Will see how that goes.