Blue Green Algae Bloom?

Has anyone ever heard of a blue green algae bloom? I recently transfered back to a pet store that I helped set up and a lot has changed. What has me stumped is that our 90 bowfront showcase tank has blue green water. Ive ruled out quite a few things. However I did discover that there is a hair/string algae floating on top of the water. Ive heard and seen tanks with algae blooms but never have seen blue green water. Ive been doing partial water changes and it seems to help but occassionally the water goes back to being a darker color. Both me and my manager are at a loss!

This tank houses are 3 koi about 6ins, one jack dempsy full grown, one angelicus botia about 5 ins, 2 plecos (one about 12 ins and the other not far behind), and one long fin rosey barb.

Any ideas or suggestions?

Both of us have been working with fish and aquariums for 6 years and this is completely new to us.

I have never seen or came across any BGA in the water column. Only on objects within the tank. Can you draw out a clear glass of water from the tank and look at it under a different light source?

Everytime we have pulled out any water its still blue green. Its weird and driving us crazy. We problem solve for a living and help out new and not so new fish comers to the hobby and we cant figure this out!

Hmmmm....this one is rather interesting then.

I would have to start with recommending a total blackout then. You may have already done it but that's where I would start.

- 25% water change
- turn off lights and completely cover the tank with a blanket for (3) days
- after blackout do another 25% water change.

Can you post up some water parms? I'm kind of interested in your NO3 and Phosphates too.

Unfortunately we cannot do a total blackout. Its in the middle of a store and we would get in big trouble. We have no nitrites or ammonia. Nitrates are on the higher side of 80ppm. Alkanlinity of about 40ppm. Hardness is 200ppm and ph sits are 6.8. We dont have a phosphate test. We do frequent water changes of 5 to 10 gallons a week. However last week I did a much larger one seeing as the sump area had been very neglected.

Hmmmmm.... if you can't do the blackout ... then your next best option may be a UV sterilizer. If it's not your nickle, it may benefit ya since it sounds like this is a business and not home use.

Your nitrAtes are big trouble as well. You need to do some big water changes to get it down to no more than 40.

Nitrates are way too high! Do a larger water change, maybe put some de-nitrating resin in with your carbon.

The algae bloom is feeding on the excess nitrate load. I second the idea of an UV sterilizer. It works the best on all microbial cloudy water blooms. I keep several on hand for my classroom tanks.

I have to agree about the UV sterilizer. I got one on ebay years ago for a similar problem.

Blackouts did not work at all, and I keep my nitrates low in all my tanks with weekly 50% pwcs, so I was, like you, at a total loss. I used the UV filter for a couple of days, and that was the end of that, for good. I did not need to leave the UV filter on the tank. I think they are a good investment. UV filters are also good for waterborne parasitic outbreaks like ich.

dude throw in tonnes of live plants, fast growers and floaters. best and most aesthetically pleasing way to rid yourself of algae. the plants will out compete the algae in the end

The water is finally clearing up after a few more larger water changes but we still have the string algae on top. We are going to be changing out the lighting to see if that works. We think the water color may of been due to the Omega One Veggie Rounds which contains spirilina. We quit feeding it to the tank and it looks to be working.