Toxicity of Cyanobacteria

[Madame_X]

Just had an experience I thought I should share as there seems to be mixed information on the subject of whether or not blue-green algae (or cyanobacteria) is toxic to fish.

I noticed a small patch of cyano on the top of my bubble ladder Saturday night. Since I use RO water in the tank and didn't have any on hand, I turned off the lights to slow down any growth and planned to do a water change the next morning.

I know most fish won't eat the stuff, but I happened to notice a little later that evening that my monster ghost shrimp was on the top of the bubble ladder eating the cyano. I didn't think anything of it and actually sort of thought it might help control it.

The next day when I did my water change, I noticed my big ghost shrimp lying on his back, kicking his legs, dying. He seemed completely healthy and was swimming around prior to when I spotted him eating the cyano. I know he was just a ghost shrimp but I was a little sad since I've had him for quite a while (as ghost shrimp go, anyway) and after surviving the 4 inch nematode erupting from his body he seemed pretty strong.

Obviously, I can't be 100% certain but I believe that the cyano ingestion killed the little guy. In my opinion, it is definitely toxic to the fish. I realize that most fish won't eat it, but since they're breathing the water I suspect that any lengthy exposure would also prove fatal.

I definitely won't wait to do a water change next time I run across the nasty stuff.

 

[Fruitbat]

Madame_X

Many types of cyanobacteria are known to release toxic substances into the water. Some species of Oscillatoria release compounds into the water that can be toxic to fish if the concentration is high enough. Oscillatoria is the most common cyanobacterium in tropical freshwater aquariums, though there is no way to tell if the one in your tank was one of the toxic species or not. Anabaena, another fairly common cyanobacterium, also produces substances that can be toxic to fish.

Most of the toxins produced by cyanobacteria are either cyclopeptides, which are hepatotoxins (liver poisons) or they are alkaloids (which are neurotoxic). There is ample evidence to suggest that these may be toxic to aquatic invertebrates (like your shrimp) and occasionally to fish.

 

[malkore]

Thanks fruitbat...that would explain why I'm losing german blue rams in a tank where I'm fighting cyano without meds (I tried increasing water circulation, and fertizing routine changes). I just decided to bite the bullet and treat with marycin....$50 worth of fish later

The rams looked fine...no bloat, no red streaking...just some less social behavior the day before they die (and in fact after death they still were vividly colored). a neuro toxic makes a lot of sense...

 

[Madame_X]

That sucks, Malkore... Sorry to hear that. I fought with cyano the last time I had it and ended up treating it with Maracyn as well. Luckily, I didn't lose any fish but after the ghost shrimp died, I'm not taking any chances this time.

Thanks for the help, Fruitbat. I had read conflicting information about cyanobacteria in the past so I just thought I should share my first-hand experience. I appreciate your knowledge on the subject!

 

[Fruitbat]

My pleasure! The only reason I know anything about cyanobacteria is that my first job out of college (eons ago!) was working in an EPA lab doing water quality analysis on some of the local lakes. Here in the Dallas area we get blooms of Oscillatoria and Anabaena in some of the lakes that are used to supply drinking water during the summer when it gets really hot. There are occasional fish kills in those lakes and in addition it gives our water a really 'unique' flavor every so often (to the point that many people won't drink it).

 

[TankGirl]

I have battled this recently and finally treated the tank with maracyn, and used a lower dose than recommended (for treating fishy disease) and treated for half the time, and it took care of the cyano handily. It was on everything - sand, rocks, everything, and it is now gone, gone, gone. I resisted trying this because I did not want to put the tank through a cycle and I am loath to use meds on my lovely N. Brichardi if I don't have to, but no cycle came to pass and the cyano is gone. I shoulda done it sooner!

I know that when treating bacteria in people if you use a low dose for half the time you don't quite kill the bacteria, and it makes it stronger, so this goes against my instict for an effective therapy, but it worked. Just an anecdote to add to the mix...

 

[Madame_X]

Tankgirl, that's about the regiment I used as well. I was so scared of killing off my good bacteria, I didn't want to overdo it. You're right, though, it worked like a charm. I never saw another recurrence until now.

Oddly enough, after removing the bubble ladder, doing a water change and cleaning the filter (which admittedly I had neglected for a couple of months), there is none of the tell-tale cyano smell in the tank. I'm going to do twice weekly water changes for a couple of weeks and see how it goes. I just hate the thought of using antibiotics if I was able to remove it in time to get rid of it.

 

[TankGirl]

Good plan. I wish now that I had picked the little bits out when it first showed up, but once before I had gotten rid of it with extra water changes. Not this time!

 

[wcdeich4]

my cyanobacteria horror

We had a bad case of dark blue cyanobacteria in the fish tank @ work & we bought a baby pleco to help eat the algae (not knowing any better) & it died a few days later. Technically since it died so soon after purchasing it, I can't prove the blue green algae was what killed it, but since the smell was so bad someone threw up & we had to break down the tank, clean objects we wanted to keep w/ bleach & treated the live plants w/ peroxide followed by Erythromycin for 2 weeks to stop the cyanobacteria from coming back - it seems like the cyano was the most likely cause of death for the fish.