# Treating blue-green algae with erythromycin



## art_b

I once treated BGA a while ago with erythromycin using a lower dose of 2.5 mg/liter for 5 days without water change. This is about 100 mg per 10 gallons. After 4 days the color of the BGA turned dark or brown.

Now, I have BGA again, but instead of dosing lower, I thought I would try another method. Instead of a lower dose for 5 days, I'll try dosing 300 mg per 10 gallons for 2 days. That is, dose on day 1; then on day3, change 25% water and repeat dose. This is explained here http://www.aquaticplantcentral.com/forumapc/algae/46892-how-get-rid-blue-green-algae.html.

I thought this would kill the algae immediately, but after a day and a half, the algae on the substrate and the glass are still blue-green. I thought they will be brownish by now. The BGA have stop spreading though.

My question is, are the BGA dead ? Will they eventually change color to brown later (maybe on day 4) ?

I will be changing 25% of water tonight, and will be doing the second dose. I just want to make sure I'm doing this right and not wasting antibiotics or creating an antibiotic-resistant algae.


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## Karebear

I have always used a double dose of erythromycin on bga, sometimes I will need to do a second dose. Just don't stop before it is gone, if you do this it will become resistant to the erythromycin.


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## art_b

On Saturday night (Day 1), I dosed 300 mg per 10 gallons of erthromycin. I did another dose last night (Day 3) of 300 mg per 10 gallons.

Today is Tuesday (Day 4). I can still see some BGA that are still blue-green in color on the substrate and glass. Are they dead ? Should I wait for a few days to see if they turn dark or brown ? How do I know if I should do another dose ?


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## Karebear

My dosage does not tell me how many mg I am using. I would dose every other day. If this does not work try minicycline or tetracycline.


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## Alex123

BGA are tough to deal with, I have a good couple months trying to get rid of them pesky nuisance. Erythromycin is a drug. Using drug to fight lower form organism sooner or later they will build immunity. Instead we should focus on treating the cause. I feel that the imbalance in the aquarium lead to this bacteria. Once it starts to take over, you are pretty much screwed. The best way is to maintain the current light setup to allow the plants to continue to grow but add a lot of new fast growing plants. I have hard water so I used elodea /anacharis. My tank had 20 percent coverage of this plant with numerous other plants. All my plants were covered in BGA. I had a healthy tank wilth a lot of anacharis plants. I clean my infested tank as much as I can, use paper towel to wipe out the BGA on the glass. Cut the infected plants with BGA and hand removed as much as I could on the plants I couldn't cut, 20% water change and then move the anacharis from my good tank over so that I had 40% coverage of anacharis. The trick is that this plant grows so tall that it grows to the top of the aquarium and block out some of the light. With over saturation of plants and cutting out small portion of the lights with my healthy anacharis, the BGA disappeared within a few days.


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## bsmith

Few causes of BGA that I have seen over the years.
a) low/no nitrates
b) poor circulation
c) your lights need to be replaced

Do any of these sound like a possibility?


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## art_b

I just put a small powerhead to add circulation of water. I'll see in a couple of months or so if the BGA comes back.


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## art_b

I don't have CO2 in my tank, so I guess when the CO2 is used up by the plants, growth is slowed down and algae may have used excess nutrients such as nitrates and phosphates.

I used to keep nitrates at least 5 ppm and phosphates to 0.5 ppm or less and it seems ok. I got my BGA bloom (and my hair algae bloome as well) when I increase phosphates to 1 ppm. I would think 1 ppm should still be ok. 

Is it possible that the ratio of N is more important in non-CO2 tank ? The BGA was triggered because I have low nitrates in RELATION to phosphates ? So if I increase my P to 1 ppm and increase my N to 10, then I would not have an algae bloom ? Will that be the same if lower my P to 0.25 ppm and N to 3 ppm ?

What do you think.


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## ER9

its difficult to say. the potentail triggers for this stuff seem to be all over the map. i battled it for near 6 months and even after correcting every possible cause it would not die. only after killing it with a product called 'blue green algae remover' did it finally go away. it hasn't returned since (couple months)


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