Hi interesting topic! BBA can be really hard to get rid of and I'm not sure using Co2 will help.
Using Co2 to beat algae is ok in some instances but not in others, the intention would be to make the plants grow faster using more of the nutrients in the water faster and starving the algae but in order to do this you have to balance 3 elements, lighting, Co2 and fertilisers. When you inject Co2 you need to increase your lighting and increase your fertilisers with the goal of making your plants photosynthesise faster. But this can also just make your algae worse. Interestingly BBA and Staghorn are pretty common in Co2 tanks and often come in areas of high flow and high Co2, so if you get your outlet pipes angled wrong it will grow.
Co2 can be great - though with plenty of risks for example overdosing can kill your fish very quickly and you will be handling pressurised containers and have one sat in your home. Though there are plenty of ways of doing it safely you just have to be careful.
In terms of the Polyglutaraldehyde - I wouldnt recommend it, if you google it or particularly the name without the poly bit it, its used for sterilising lab equipment. In aquarium use the plan is to basically act as a toxin in a low dose to kill off single cell organisms and the effect to fish and plants is not plainly explained anywhere but my imagination runs a bit...
How bad is the algae, what is it on and what is your set up like - eg which fertilisers were you using, what kind of light and how longs its on? How dense is your planting and what kind of plants do you have already? Pics of the tank might help too
Wills
This time is the 3rd time we've had BBA, previously we just did a deep clean and dipped ornaments and plants in hydro peroxide. It was spreading like wildfire. This time, it was spreading very slow, barely at all, and it was sticking only to one plant. An
anubias nana (I think, looks like it, came stuck to half a coconut shell ages ago and I didn't buy it so not sure). I took it out two days ago and dipped in hydroperoxide dilution, so you can't see the algae right now.
Lights: I was told my lights are too bright, which aids the algae, so I got duckweek. Since I still had the algae, I reduced lights to 6 hours max. Before, we'd keep it on morning - night, about 12 hours. Evening time we enjoy watching the aquarium, but now I turn it off around 6pm. I turn it on early, because I have to feed the fry first thing in the morning.
Main plant I have which was 1 out of 5 which survived and spread is:
Hygrophila Polysmerma, as you can see it is mostly yellow as it grows taller. I don't fertilize anymore as I felt it was just creating more algae and the plants weren't improving. It is covered with a combination of indian almond leaves' residue which passes around the tank and attaches itself, and traces of black beard algae. There's a bit of BBA on the live rock also. Other than that, it's not spreading.
Most recently,
Nymphaea Rubra Red Tiger Zenkeri Lotus was introduced as a bulb and has taken off also.
The article I read :
https/fishlab.com/black-beard-algae/#:~:text=Nope, black algae is not,in the long flowing hairs
Suggests increasing Co2 with Seachem flourish excel, and I considered this a good option if it also helps my plants.
I'm very aware using tap water is the cause and is high in phosphates.
I was using the TNC fertilizer and plants were thriving but so was green algae, I then stopped and used a phosphate reduction product called
Red Sea algae management, phosphate and nitrate control when we had way too much green algae.
.
I then switched to
TNC LITE without nitrate and phosphate
I've never used additional CO2 and it's my first time considering it as I want the plants to be healthy again. But as I can see from reviews, the SEACHEM flourish excel isn't carbon, it becomes carbon slowly, so it should be fine? What do you think?
As for my water flow, I have
fluval U3 on low steady flow, sometimes I change to deep flow to move the water deep in the tank, sometimes I switch to the top setting to oxygenate the tank but usually I set it to a low setting, steady setting as I can see it blows the fish around otherwise.
Previously I had the fluval 307 canister filter (when we had MORE black algae the first two times it showed up) so maybe higher flow did increase it. That filter stopped working and I got the Fluval U3 as a temp but works fine so the 307 is in the shed, U3 having lower flow might be helping it not spread then?
Also tried mollies for black algae but then read they need to be very underfed to go for the BBA.
Plants start off healthy and green when young but yellow as they grow taller and snails eat lower leaves .
separate issue lol
ALSO: I've started vacuuming the gravel, but I've also wondered, does this take nutrients away from the plant's roots?
Here are photos:
THIS WAS THE BBA BEFORE I dipped the anubias (I think it's anubias) in hydro peroxide. Actually it was worse, two leaves were covered in black so I just cut them off.
Excuse the sick fish, this was a recent issue hence the photo now being sorted. I have no other photos of the BBA so had to use it.