Is it BGA? What kind?


Junior Poster
Dec 4, 2007
Dear friends, please, is this BGA? If yes, which kind? And how to fight against it?
I tried to find out exactly what king of algae or BGA it is, but I was not successful.
Some people told me it is BGA, but all pictures of BGA I have found are different. This algae does not smell, you can remove it by vacuuming. I looks that it does not grow on plants or on any surface like algae, but only floats and catches in plants like Egeria, Riccie ...

I do everything - bottom is clean, regular water changes, filter cleaning ...

Water parameters are:
Tank: 125 liters (33 galons)
CO2: yeasts
pH: 6,7-6,8
kH: 6-7
gH: 12
Fe: about 0,5 mg/l
PO4: 0
NO2: 0
NO3: 10 - 15
NH3/NH4: 0
Lightning - 2x 28W Day and 28W Natura

Sorry for my English. It is not my native language and I have not spoken very long time :)

Thank you very much for your help.



Plant Guru Team
Lifetime Member
Sep 23, 2007
South Florida

It looks like a thread algae to me.

Two questions:

1. Are you running 56w of 'Day' AND 56w of 'Natura' at the same time? I didn't quite get how much light you have...

If so, this is a lot of light for a 33 gal tank. 132w / 33 gal = 4 wpg which is a lot.

2. C02 by yeast does not always supply constant c02. This and the lighting may be contributing factors.

Hope this helps.


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
You say you have zero phosphates. You should have about 1 ppm of phosphate, not zero. I assume you are fertilizing the tank. If so, you should be adding nitrates, phosphates, potassium and trace elements, using a method that you can follow routinely, always dosing the same amounts. Many of us use Tom's Estimative Index method, which you can read about in one of the forums here. When you get the fertilizing going and keep the amounts you add about the same every time you add some, the plants should grow at a steady rate, which will discourage algae from starting to grow.

You also need to keep the same concentration of CO2 in the water during each time the lights are on, so you need some way to determine that you are doing that. Using a drop checker is the best way I know of to do that.


Junior Poster
Dec 4, 2007
Thank you for your opinion. I use Sera Florplant. There should be all, but it is not as good as PMDD probably. It would be better to mix it by myself. Next step. I know that my phosphates should not be zero. But I am not sure that P is not there. I have only test for PO4. My tap water has 0,25 mg/l PO4(about 1 mg/galon?) and I change 1/5 - 1/4 every week. Tap water also has NO3 25 mg/l (100mg/galon?). I also add 15 fish (small Microrasbora Galaxy). Light is 56W together (1x28W Day and 1x 28W Natura, 12 hours a day). My mistake. I am sorry.
I have a lot of plants - about 15x Limnophila, 18x Rotala, 4x Anubias, some Valisneria Spiralis, 3x Pogostemon helferi, 3x Cryptocotyne ...

As I wrote - I have not problems with plants, but with one kind of algae from pictures. I am not able to identify it, so it is very bad to fight with it. Could someone tell me exactly what kind of algae/BGA it is? Here is another photo from today.

Thank you.



Tom Barr

Staff member
Jan 23, 2005
Looks like Rhizoclonium or Oedogonium(or both) with soem diatoms attached.
I'd say clean the tank good, stabilize the CO2 add ferts consistently, add Excel also.
So water changes are also in there after you clean, prune it off etc.

It should not be hard to get rid of with good care.

tom Barr


Junior Poster
Dec 4, 2007
Thank you Tom,
I am sure it will not be hard to get rid of it when I know what it is. Unfortunately, I showed my pictures to several people and they told me that they see BGA. When I told them that BGA looks different, they told me that there is a lot of kind BGA :-( Thank you for your help again.

You are right with water stabilization and CO2 (pH). The biggest difference between aquarium and tap water is NO3 and pH. Aquarim is about NO3 10 mg/l and pH about 6,6 - 6,8. Tap water is NO3 25 mg/l and pH 7,5!

Algae grows mainly two days after water change. So, I think that pH increase a lot after water chang (CO2 lower) and I also add a lot of new NO3. After one ot two days, when pH is about 6,7, algae stop growing. It seems to be logical. I only did know the reason. I will probably build system with pressure cylinder and CO2 sensor which would keep CO2 stabilized much better then now. I will also try to optimize fertilization by mixing own PMDD.

Nice to meet experts