Blue-Green Algae (Cyaobacteria) on sponge filter

Hello again everyone,

This time I have another algae question, and I can't seem to find anyone with the same issue after a quick search.

I have been dealing with BGA in my 20 gallon tank for a couple weeks now, and while it hasn't been spreading like wildfire as some people report, I can't seem to get rid of it completely. The tank is only a few months old, but I haven't beeen having problems with any other algae recently, just BGA. I have been siphoning out all the bits I see from plants, substrate and glass with a small-diameter tube every day (I would recommend this, smaller tube has pretty good point suction and seems to be able to get the sheets of BGA lifted off things, and it also doesn't suck up that much water, so I have much more time to make sure I get all the bits before my bucket fills up. This also ensures that none gets released back into the water, unlike advice I have seen on other forums to use a magnetic algae scraper or things like that)

My main issue is that I keep finding BGA coating my sponge filter, and after just a few days it can cover and clog up good portions of the sponge. I have also siphoned all I can off the sponge, but it seems like the coarse texture is allowing it to cling on much better than it usually does. It doesn't come of neatly in sheets like it tends to do with plants, and each time I clean it, I can tell there is still green stuff in the pores of the sponge.

So, my question is, should I disinfect the sponge to get rid of the BGA and let my other filter do all the work for a few days while the sponge re-establishes good bacteria? Or is there some way I can get rid of the last bits without killing the bio filter in the sponge?

Also, my final question: the BGA seems to be slowing down, so in your experience, will it eventually become under control when the tank is fully established and balanced?

I am having hard time with a 30 gallon tank with this stuff along with a couple other issues. What seems to work for me keeping the stuff at bay is a combination of water current, surface aeration & water changes once a week. I did have to medicate just to irradiate the majority of the BGA that I couldn't get by cleaning...

I can answer one of your questions (maybe two). I started dosing my 10 gallon which had BGA with Flourish Excel. It started going away (seems like in a couple weeks). It had originally grown on surfaces like the substrate and sides of tank, as well as my marimo moss ball (I threw that out) and my crushed coral bag (resting on the substrate).

I've kept up with dosing Excel, not necessarily daily though and I've not had any BGA since it went away.

If you're lucky, excel will get rid of it. If you're lucky, over-dosing with potassium nitrate will get rid of it. I wasn't lucky with either of those approaches.

And no - having a "fully-established" tank won't necessarily matter. This stuff may go away on its own, but it most likely will not (in my experience).

I'm inclined to agree with theChad's approach - keep it well-aerated and keep do more frequent water changes after treating with an antibiotic. A 3 - 4 day blackout may help as well.

My approach was nuclear war - I won, but I broke the whole tank down to do it, tossed the substrate, and soaked everything in super hot water.  

Only way I have ever won the war with "bga" Cyanobacteria was a 2 week black out of the tank, after first doing a large manual removal the stuff. It sucked, but it worked. Just an option. Good luck.

The strange thing is, unlike other people, I don't have it growing back within a couple days, it seems to grow very slowly in my tank (so far)... if I get all of it that I can see, it will take a couple days at the least before I notice it popping back up again.

I have stopped using excel within the last month or two, so perhaps that is the factor that caused it to start popping up. I would like to identify the reason it keeps growing, though, instead of just relying on excel to keep it at bay.

I put a couple of catappa leaves in the tank; since I have heard they have "antibacterial" properties because of their tannins, I am hoping they might help keep the stuff growing even slower than it has.

I might just need to start doing more water changes to keep nutrients balanced, I have been purposely slacking on that front to see how the tank would cope, so maybe this is a sign that I shouldn't have tried that out, haha

Thanks for the help by the way, everyone, I appreciate the suggestions. I might just end up breaking it down like pb did, since I have to move soon anyway.

Here's a little update:

The leaves have definitely stained the water pretty well with tannins, and hopefully this will have an effect on the bacterial colonies that I can't get to/can't see. I'm sure there is still a lot of it in there, even with siphoning it out, but maybe this will prevent it from continuing to spread.

I used Erythromycin to get rid of BGA couple weeks ago. The process last 4 days, and BGA was completed gone. I believe this also killed many bacterias

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Maybe this will help? I would follow Roy's recommendation