I recently had an outbreak of Blue Green algae in my 20 gal tank. The algae was always there, but only a little on the back tank wall, and a few spots on the sandy substrate. When I went on a trip for 10 days, the tank was without light for undetermined period of time (my little boy was "in charge" of feeding the fish and turning the light on and off!). Any way, when I got back, the whole tank was cover with smelly sheets of BGA: everywhere, on the sand, on the rocks, on the leaves of my anubias, and practically killed off all my java moss...I immediately did a large water change, tried to remove and suck out the BGA as much as can, only to see the next day everything is back to the same way. I cleaned them again and putting in lot of Hygrophilia polysperma that I have growing like weed from another tank, hoping they will outcompete the BGA. Well, the hygrophilia grow, but their leaves are covered with new sheets of BGA everyday. The tank is still not improving and very smelly...
I start doing research on BGA on the Krib and aquaria newsgroup. My challenge of fixing this tank is: it is the home of my elephant nose for the past 6 months, and of about 40 less-than-one-week-old fancy guppy fries. (I'm still amazed at how the poison from the BGA have not killed any of my sensitive fishes).
I didn't like the idea of antibiotics that much, and "blackout" was the reason of my BGA problem, so I would not do it. I then read about "hydrogen peroxide" method and determine to give it a try, since I have just bought a 3% concentration bottle for my kid's scratches.
Since I have e-nosed and fries, I decide to put in only 6 teaspoons (of the 3% concentration) for my 20 gallon at about 8PM that night. I let the light on for another 2 hrs and went on to sleep. The next morning, I saw a big improvement on the BGA situation: no new BGA anywhere, and existing ones are turning grayish green, appear to be dying. The water is a bit milky though, so I did a 20% water change. I carefully observe the fish, looking for any kind of stress, but they are all acting normal and eating well. The hydrophilia are growing better (no more BGA covering their leave). After the water change, I decided to put in another 3 teaspoon of Hydrogen peroxide. The day after, more BGA died off and I did more spot removal of existing dead BGA.
I decide to stop the treatment at this point since my plants are now appear to be winning and I don't want to take any more chances with my elephant nose and the fries. There are still area of green (healthy?) BGA on the back tank wall that I never had easy access too, however, the amount of BGA seem to be much less than I ever remember for this tank.
All of this was about a week ago and my tank, fishes, plants all appear to be normal. I'm not big on water parameter measurement, since I don't own many test kits. I guess so far, I'm lucky with good tap water in my area. I only observe my fish very carefully everyday: if they dont eat or don't look good, then you'll have a problem, no matter what water parameters...
In summary, I have controlled the BGA in my 20gal tank with a total of 9 teaspoons of Hydrogen Peroxide in about 36 hrs period. I understand that this treatment, like all algae treatments, is not a silver bullet for extermination of algae, but only to give you a chance to bring your tank to managable level.
If you don't want the atibiotic path, I strongly recommend you look into the Hydrogen Peroxide solution, which seems to work wonder for me (search on the Krib and aquaria newsgroup for hydrogen peroxide and BGA)
Regards,
