I'm starting to have a problem with Blue green algae, slime algae, or Cyanobateria which is a bacteria, I found the treatment course listed below that I'm going to try and wanted to post it here and report my sucess afterward, we'll see.
Also I did not write this but you can see the full article with credits here.
The followin is my suggestion for battleing blue-green algae:
First make sure that it is blue-green bacteria and not the "normal" algae. Remember that erythromycin is ineffective on anything but bacteria.
Add 2.5 mg/L erythromycin. If you have a protein skimmer, turn it off. I believe it will inactive a lot of the antibiotic through coprecipitation with protein. It will, however, be very usefull later.
Add 2.5 mg/L erythromycin.
Now you should see a lot of dead blue-green bacteria floating around in the tank. Increase filtration (a second mechanical filter if possible) to get rid of it. If you have a protein skimmer, turn it on. The critical thing now is to get rid of as much protein (dead bacteria) as possible to avoid a peak of ammonia.
Most blue-green bacteria should be dead by now. Try to clean out as much as possible of the dead stuff. I use a jet stream of water from the outlet of a canister filter to remove it from plants and decorations. Combined with the second mechanical filter, this works fine for me. Let the filter work for a couple of hours then make a 50% water change. Add 2.5 mg/L erythromycin.
Wash the mechanical filter at least once a day. Keep check on ammonia and nitrite but do not change any water unless absolutely necessary. The extra filter can be removed as soon as the water clears up.
Make a 30% water change. Add 1 mg/L erythromycin.
From now on, resume your normal maintenance.
The concentration I use is in theory a bit high and getting up where it should starts having an effect also on G(- ) bacteria. When I started using erythromycin I had problems using lower concentrations in the tank. It was not very effective. It might be time to check it again.
One word of caution. Only use erythromycin when you really need it or you might end up with blue-green bacteria resistent to the antibiotic.
My practical experience of using erythromycin to battle blue-green bacteria is limited to my own few tank (and some friends). It would be interesting to get some feedback from people with experience (good or bad) of battling blue- green bacteria (with or whithout erythromycin). I would of course post a summary of the response.
I did use the above method to remove Cyanobateria aka Blue Green Slime Algae and it worked very well, I never did experience and ammonia or nitrite spike but my nitrates stayed very high and I did not dose at all during the treatment period but by the 8th day nitrates had fallen off to 1 or 2 ppm, my tank is 150 gallons so a larger volume of water most likely played a role in this, I also didn't need to run a second filter but again volume and I already run 2 filters. However the tank did suffer some serious side effects, I lost 3 fish to Pop Eye and have a fourth fish in a hospital tank, I also had a 6 year old SAE come up with a bloody red dorsal fin but I'm not sure if this was a underlying bacterial infection like fin rot, etc. but he is too large for my hospital tank and I will just have to play it out as it comes, he also could have bashed himself into the glass or driftwood as oxygen levels got low in the tank and if I ever find out I'll let you know. There is also a one inch layer just under the top crust of the substrate that has some white substance speckled through out and it was not there prior to the treatment but this tank is very old with the original substrate so anything is possible.
Even with some frustrations I would recommend this treatment but make sure you follow the rules to the letter and be ready for any situation to arise, good luck.
The week after, now the total is 6 dead Rummy's plus one has been in the hospital tank for 10 days with Pop eye and survived, and the SAE is still kicking but not fully recovered.