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Cyno + SPS not doing well....


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My 90G SPS dominant tank has been doing well for a couple month until about last month. Problems started to pop up...


Things were fine until I purchased 4 green chromis, 2 anthias, 1 red star, and 1 sand sifting starfish. First pH started to hike, which I had no idea why. I added vinegar to lower it, and I added too much. pH lowered to 6.XX immediately, and I used kalkwasser to increase it right after that and it went back to 8.1X. Then I started to doubt my pH probe so I bought a new one and found the old one was off. After calibration the old one still can't match with the new one.


During the pH spike, the pink birdsnest generated those "bubbles" on it's skin, and burp, they broke eventually, exposing the skeleton outside. They stopped when the new probe was on and pH fell into acceptable range.


However, during this time, cyno started to grow, crazily. They basically covered the surface of many stones. Many SPS corals were damaged. Their tips started to have STN. And they started to brown up. Acropora, monti, except for birdnest, had tip burning. This stopped when I bought a dual reactor from BRS and plugged it in with Phosguard and ROX.


Now I've tested a few times by HANNA; the result for phosphate stays around 7~9 ppb. I used to have this figure without any cyno. I'm so puzzled why the cyno still are here despite I suck them out every time I do water change.


suspicious factors as following:

too many fishes. problem wasn't there before I added 6 new fishes

sand sifting starfish. it eats good things in the sand bed?



cheato started to grow very fast. It used to not grow at all.

some SPS browned out

Green Birdsnest's started to have STN from bottom up. It's a small colony.

Phosphate was once 45 ppb, reduced to 7~9, while cyno didn't seem to change that much.

water flow is generally strong

I've been doing heavy water changes since the case happened


I'm planning to move all the rocks out and sell the majority of fishes.

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How much are you feeding the tank daily?


Do you have numbers for your Alk, Ca, Mg, and pH now? I'm assuming your ammonia and nitrite are zero and your nitrates are under 10ppm?


How large of water change? Are you using RODI water? Have you tested the numbers of your new source water (I just found a bactch of salt I am using had an Alk of 6 so that was a problem that I had)


Generally cyano has a root cause. But fixing the root cause does not always remove the cyano. Cyano is one of the older bacterias in the world. It has the capability of doubling itself in a 20 minute period, which means if you pull out 99% of it, your ahead 3 hours, because it can catch up that quickly.


There are ways to treat cyano, the two common methods involve a treatment that utalizes eurothromycin commonly sold in stores as chemi clean in the hobby. The other is to turn the lights off of the tank completely for 3 days as this amount of time without light will completely kill cyano. In most cases I recommend the second of the two as a healthy tank can easily go through a 3 day dark period and come out just fine. You however do not have a healthy tank so the chemical treatment might be your better option.


The amount of fish in a tank (unless it is to few) is not going to bother SPS. The amount of food and unremoved waste are the problems. If you are able to feed less often or even the same amount but broken up to several times a day, it might help you out as well.


When you say waterflow is generally strong, I am not sure how that translates as it is a relative term. I have a tank that turnsover 120x an hour, I consider it strong. It's on a wavemaker with alternating pumps through the day so the flow varies and nothing sticks in the rocks. Are you upwards of a 100x turnover, are you closer to 30x, 50x? Actual numbers help me to help you so I am not making generalizations. FWIW most people think the flow in my tanks is to high, so you don't need to match it but I'd love to get a better idea so I can try to help you.


Can you post a full tank shot so I can see the tank, and where the powerheads are?

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Cyrano is a bacteria, not an algae. If you live in the Willamette valley you will get it periodically. It's just a fact of life. The vinegar can feed it. Actually any carbon source can feed it. That's why when carbon dosing it's necessary to go slowly and when the cyano starts, you back off. I personally have it now and then and I treat my tank a couple of time a test with Chemi-Clean. Knocks it out in 48 hours. Requires a 20% water change immediately following the treatment. Cyanobacteria is airborne, there really is no getting around it unless you live in a bubble. The wild ph swings are probably the root cause of your coral issues. Back of on feeding, check for dead spots in the flow and buy a bottle of Chemi-Clean.

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first I would stop messing with things. first rule to sps is DO not chase pH numbers they are irrelevant. second I would think that the cyano came from increased nutrients or your carbon dosing. the best thing to do is maybe some water changes and try to let things stable out a bit. nothing good with sps comes fast and that goes for fixing also.

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As many have said, pH is irrelevant and shouldn't be chased. I don't really see any use for a ph probe unless it's controlling a Ca reactor. Your SPS are all pissed because you reacted so harshly. Corals adapt to slow change much better than quickly dosing things. You likely spiked your Alk dumping in kalk and did most of the damage there.


For cyano, use some chemi clean. The lights out method never works, especially if you have it bad. Just make sure your skimmer is off or wide open and put an airstone in the tank and it works great.

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