Erythromycin For BGA

[itafx]

Last Thursday, I started an experiment in my 20 high gambusia fry tank. It has been plagued with BGA. It was so bad the plants get covered and there were webs of cyano between the branches and leaves. The substrate had a carpet of thick BGA covering, perhaps 90% of the area. This happened before and I cleaned everything and did wc but it came back

I finally broke down and ordered an algacide from aquariumplants.com that was supposed to do the trick. When I got it and read the label I found that it was erethromycin.

I dosed according to the directions, turned off the light, and put some black paper on the back of the tank to help shield the tank from sunlight.

Two days later, the BGA seemed to be halted and less healthy, but still there. The fry were fine. I removed and washed off all the plants and replaced them. I also skimmed, washed, and returned the sand.

Now it's been 5 days since dosing. The tank is squeaky clean and the fry are still fine. I'm still watching to see if there are any deleterious effects on the fish or if the BGA comes back, but so far I am convinced it was effective and worthwhile.

I realize some will be concerned about creating resistant strains. To that I would apply an analogy with a patient who is dying of a massive infection. At that point the issue of resistant strains pales in comparison to the need to save the life of the patient.

I would be interested in input from others on this experiment, particularly from folks who have actually tried Erythro as opposed to opinions derived from reading literature.

[Zezmo]

That is considered the standard and recomended chemical solution for BGA. Normally Marycyn is recomended, as it is the same antibiotic. It will wipe it out, but it will not keep it from coming back.

[itafx]

I guess the spores are in the air and tanks could always be susceptible. If I can get my ecosystem back on its feet, maybe it can resist BGA better in the future.

[An t-iasg]

I have used erythromycin, along with a blackout, on my tank 3 or 4 times to get rid of the horrible BGA. It worked like a charm. I didn't even see any "dead" BGA after I removed the blackout garbage bags. I finally fixed the problem by re-directing the flow from the powerhead.

[itafx]

That sounds great. How long was the blackout? Did you take the covers off during the blackout to look and see if the fish were in any distress? What did you change about the flow that made the BGA go away permanently?

[malkore]

eurythro should be the last step taken against BGA. As with humans, excessive use of antibiotics in a fish tank will result in stronger, resistent strains of bacteria.

BGA treatement steps (assuming that cleaning off all plants, decor, vac'ing out the floating BGA, and doing a massive water change didnt' help):

1. test NO3 - if NO3 is low or 0, that's the reason you have BGA
2. if NO3 is fine, do a 5 day total blackout of the tank. the fish won't starve...or just feed them once after 3 days. NO LIGHT ALLOWED
3. when all else has failed, then medicate.

[An t-iasg]

Yes, erythromycin is a last resort. I had rather mild BGA in another tank and a 7-day blackout (no erythromycin) took care of it quite well too.

The tank I was referring to in my last post just had gobs of BGA-cyanobacteria. I have pressurized CO2, and the nitrates were not bottoming out. I would do a water change and syphon the BGA out (it does vaccuum out pretty easily) and three days later the tank was just draped in the cyano again.

Some people report success with a three-day blackout. Since mine was so persistant, for my final blackout and erythro treatment, I did a water change and then just draped the tank for the whole week. You should do a 50% water change before and after the blackout. I wrapped the tank with black garbage bags - sides and top. I took the time to snugly wrap the bags around the corners and make sure the areas of the tank where the filter tubing came out was adequately covered too. I even closed the blinds and put newspapers over the window (it's a small window).

I used 250 mg of erythromycin every other day during the blackout. I let it partially dissolve in a cup of water and then poured it in. I made a "flap" out of the garbage bag on the top of the tank to easily let me open the glass lid for a few seconds.

I didn't have fish in the tank at the time. The tank was a few months old and it always had this cyano problem almost from day 1. I didn't want to get fish until I got the cyano to go away for good. I think if I had fish in there, I would have fed them once during the blackout, very sparingly. Others have reported that it's hard not to peek on the fish, but they were just fine.

I also didn't do any ammonia tests since no fish were present. Since the tank was never cycled (at the time) I don't think an ammonia spike from the death of cycling bacteria would have shown up on the test. However, the decomposing cyano may have caused a slight ammonia rise. I'll never know since I didn't test, and again the reason was that no fish were in the tank.

I can't believe how easy it was to fix the cyano problem, thanks to suggestions of members here! I have pressurized CO2, and the diffuser was misting nicely, but the mist was not directed through the tank. I moved my water pump (it seems silly to call it a powerhead since it's a little Marineland Mini-Jet, but it functions as one) to the top of the tank instead of the bottom. I originally aimed the flow at the bottom front of the tank since most of the cyano was showing up there, but I moved it to the top near the waterline. I put the CO2 diffuser under the pump's intake, so the pump sucked in all the little CO2 mist bubbles and blew them out near the top of the tank. The filter output is beside the pump also, so the CO2 is being ejected into the faster area of waterflow, where it is carried all over the tank. I do need to point out that this is a 10 gallon tank, and there is no "strong" or "fast" flow but the filter and powerhead do combine to give the tank an adequate flow and eliminate dead spots. For my tank, eliminating the dead spots of water flow, maintaining a good CO2 dispersion all over the tank, and maintaining the nitrate levels (especially important since there was no fish in the tank at that time) was the key for me to eliminate the cyano.

Edit - Nice to see you, malkore!

[LindaC]

I've been having problems off and on for months with BGA in my 10 gallon tank, I have not used Marcyn due to fish in this tank. I have blacked out the tank twice already and it has cleared the BGA but it always seems to come back.

I do have a powerhead in this tank and it is at the top right near the water level but it does not seem to help. I've tried moving it down only to have the small plants in front blow all over the place. I've tested my nitrates and they are always above 20 ppms, so that's not the problem. I'm at a loss as to why it keeps coming back, it's so frustrating. I do a 50% water change once a week and whenever I see the BGA on my subtrate, I go in and take it right out, but I'm afraid it might get ahead of me again and I'll have to do another black out.

Did I say, I hate this stuff, it has a horrible smell and it's so invasive.

[itafx]

What makes the nitrates go away?

[An t-iasg]

In a tank with live plants, if the lighting is high enough to drive photosynthesis quickly, the plants will use up the nitrates. If your fish bio-load is not heavy enough to supply the plants, or your tank is heavily planted, then the plants will use up the available nitrate quickly, causing the nitrate levels to fall. I believe a level of 10 ppm is necessary to ward off cyano. If your levels are consistently below 10 ppm, you will probably experience a cyano outbreak. There are supplemental nitrate fertilizers to add to your tank, if necessary, to keep the nitrates from "bottoming out".