Tropical Fish Keeping - Aquarium fish care and resources

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Hawkian 04-09-2010 02:43 PM

Something doesn't add up here (IMO)
So I have a fish tank with the following water parameters:

gH: 80 mg/L
kH: 60 mg/L
pH: 6.5
Ammonia: 0
Nitrites: 0
Nitrates: ~ 5 ppm

The tank last September and since then has kept these same water parameters very steadily over the better part of the last year.

After the cycle, I started buying live plants which in my view adds to the overall look and feel of the tank.

And then Cyanobacteria (a.k.a. BGA) appeared. I have been fighting this nuisance for the last 6 months and many scrubs and water changes later I am still having problem getting rid of it. The stuff has literally killed off all my live plants and I've even removed ALL the gravel from my tank at some point and boiled it for 15 minutes before adding it back in. I've tried the blackout way for 3 full days to no avail.

This is now 1 month later. My tank is still void of plants because I do not want to add live plants knowing that the BGA is still present in the water. I do a 50% water change twice a week, giving the tank and the filter and filter media a thorough scrub every time in tank water. This fish tank is probably the cleanest tank out there and while there is little visual signs of cyanobacteria, still the BGA remains present in the water. The tank is in the basement where natural light is non-existent so this is not the issue.

So on to my question before I start ranting some more and bore everyone to death:

I have read that having a level of nitrates around 20 ppm may actually help in eliminating the BGA.
  • Is this true?
  • And if so, how does one get to have nitrates levels that high by performing weekly water changes?

I feel like I am missing some info here because based on Byron's article about planted tanks, I was doing everything right and still this @#% BGA persists... so something is clearly amiss...

Byron 04-09-2010 06:11 PM

I am of the school that treats cyanobacteria as an organics, not a light, issue, though obviously it needs light to live; but organics cause it. I have written elsewhere I think that I have heard some situations are more likely to create it, such as crypts. And I do have it only in one tank, the one with crypts. I had what I thought was a severe infestation in November, and by simply removing it by hand every week as best I could during the partial water change (it came back completely within 3 days), it did suddenly stop in late December. I still see the odd bit each week among the floating plants which are thick in this tank and I remove it. And the tank is high in organics; pH 5, zero hardness, thick with fast-growing plants, few fish though. And I only fertilize once weekly in this tank which seemed to also have helped remove it in December when I went to once weekly.

I have copied the following two passages from other sources I use; not mentioning which because they are forums themselves. They offer some ideas worth considering; colours are only to differentiate the two articles.

Treatment with 200 mg of erythromycin phosphate per 10 gallons of water will usually eliminate blue-green algae but some experts feel it may also have adverse effects on the biological filter bed. If erythromycin is used for treatment, ammonia and nitrite levels should be carefully monitored.

It is common in two different circumstances:
  • In very low nitrate situations, BGA will sometimes form. It is able to get nitrogen from the air. I've seen BGA several times right near the surface, under the filter return. In this location, it can obtain nitrogen from the air. Adding Nitrate to maintain a 5-10ppm nitrate level often eliminates the BGA.
  • BGA has also been found to occur in situations where poor water currents in the tank result in low O2 levels in portions of the tank. In these cases, increasing water movement will often eliminate the BGA.
No fish will eat BGA. As stated above, BGA is a bacteria. Some studies suggest that BGA contains toxins. This would explain why nothing will eat it. As a last resort, antibiotics have been used to clear BGA. But antibiotics should be used carefully. They can damage bio-filter bacteria, and mis-use of antibiotics can be harmfull to the fish.

karjean 04-09-2010 07:38 PM

Thanks Byron for the passages.

jeaninel 04-09-2010 11:55 PM

Uggg...BGA can be very frustrating to get rid of. All it takes is one little cell left over for it to reoccur. I had it a while back in one of my 10 gallons (which, by the way, had crypts in it...hmmmm.) It was growing on the sand substrate and a little on the driftwood. I kept scraping it off the sand and DW but it kept coming back. It finally went away (and did not come back) when I had to treat the fish with an antibiotic.

Hawkian 04-10-2010 04:36 PM

Hey Jeaninel... was the antibiotic Mardel's Maracyn by any chance?

jeaninel 04-10-2010 09:48 PM

I don't was a couple years ago. I've only ever used Maracyn, Maracyn2 or Furan 2. Maracyn does contain eyrthromycin so it may have been that one.

Byron 04-11-2010 09:54 AM

Maracyn can be detrimental to plants. I had reason to use Maracyn once for a stubborn protozoan and all the Echinodorus tenellus turned to mush, along with the red-leaf swords; E. bleherae seemed to survive. The pygmy chain swords came back after a few weeks with major water changes, but the red-leaf swords never regained their former glory. I did some research at the time and discovered evidence that this was a frequent result of certain anitbiotics.

Of course, even more serious is the use of unnecessary antibiotics on fish. I understand the temptation we all have to use something when we are facing such issues, but just be aware of the possible consequences.

Byron 04-11-2010 10:40 AM

Came across another bit of info on cyanobacteria with a bit more detail:

Blue-Green Algae
even though it's commonly called blue-green algae (BGA), it's not classified anymore as one. This "algae" is actually cyanobacteria, a form of life that has both animal and plant characteristics. It forms slimy, blue-green, sheets that will cover everything in a short time and give off a strong, characteristic scent. If left to over-run the tank, cyanobacteria may kill plants and even fish. It doesn't stick and can be easily removed manually, but will return quickly if the underlying water quality issue is not fixed. It can be treated with Erythromycin and other antibiotics, but this method should be done carefully since it might affect the nitrifying bacteria in the gravel and filter, and improper use of antibiotics always brings the risk of developing a more resistant strain. When the BGA gets killed by the algaecide it will start to rot and through that process it will reduce Oxygen levels in the tank. Since the nitrifying bacteria needs O2 to transfer ammonia/nitrites into nitrates the nitrifying process will slow down. If algaecide is used, make sure to test the ammonia/nitrite levels. Remove all the visible algae to prevent it from rotting in side the tank.

Some aquarists use the black-out method previously described, where black bags are wrapped around the tank for 4 days and held in complete darkness. It is advisable to raise NO3 levels to 10-20 ppm before starting the black-out period. Manually remove as much BGA as you can before the blackout, and dead matter after the blackout.Egeria densa (Elodea) and Ceratophyllum demersum are good plants to have in a tank, since these plants are known to secrete natural antibiotic substances that can help prevent BGA. Establishing lots of healthy, fast-growing plants from the day you start the tank, dosing the nitrate levels to maintain 10-20 ppm, and vacuuming the gravel to keep the tank free of decaying matter is the best way to prevent this "algae". BGA can be found in aquariums with very low nitrates because it can fix atmospheric nitrogen. BGA seems not to like high CO2 levels and stronger water currents.

Hawkian 04-11-2010 11:27 AM

This is great info Byron! Thanks.

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