Blue-green algae and erythromycin
by -at-Tony.Clementz.mikrbiol.lu.se (Tony Clementz)
Date: 7 Feb 92
Newsgroup: rec.aquaria

I’ve followed the postings about blue-green “algae” and Maracyn (erythromycin) the last few weeks and the following is an attempt to review some facts about erythromycin (the active ingredient in Maracyn) and blue-green algae, with special emphasise on the use of erythromycin for treating blue-green “algae” infections.

BLUE-GREEN “ALGAE” IS NOT AN ALGAE.

Thats right. The correct name is blue-green bacteria (or cyanobacteria for those latin freaks out there). So without going into a lot of details, blue-green algae is a bacteria so an outbreak of the stuff in your tank is actually an infection.

It is important to know that blue-green bacteria comprise a large and heterogeneus group of organisms. Not even the color is the same. Some are green, some blue-green, and some are red. They can be found almost everywhere in nature. They are usually more tolerant to extreme environments than “normal” algae and can be found in hot springs as well as saline lakes. Drying your gravel and tank is subsequently not an efficient way to get rid of them. Some species can even be found in the middle of the dessert. Blue-green bacteria efficiently absorbes light between 550-700 nm, which is roughly the same as for plants and green algae.

As we all know, they thrive in warm water, rich in nutrients. However, many blue-green bacteria is not dependent on nitrite, nitrate, or ammonia, since they can use molecular nitrogen (nitrogen fixation). This all leads to the well known conclusion - once established in the tank, they are a pain in %&#-%&. I wonder how many potential aquarium hobbyist has been lost because their first tank became covered in green slime within six month.

GRAM-NEGATIVE AND GRAM-POSITIVE BACTERIA.

Bacteria can be divided into two groups, either Gram- negative (G-) or Gram-positive (G+). This classification is based on if the bacteria stains (+) or not (-) in a special staining technique - the Gram staining (invented by Christian Gram). Positive or negative staining reaction reflects a fundamental difference in the structure of the cell wall of the bacteria.

ERYTHROMYCIN IS AN ANTIBIOTIC.

Erythromycin is more efficient towards G(+) bacteria than G(-). It is one of the safest antibiotics, meaning that it does not affect plants, fish or animals. Blue-green bacteria belongs to the G(-) bacteria but it is a special case with respect to sensitivity to antibiotics (i’m on thin ice here, but I think I am correct). They are more sensitive to erythromycin than other G(-) bacteria. Fortunately, the bacteria important for the nitrogen cycle (your biofilter) are of the G(-) type and are much less sensitive to erythromycin than the blue-green bacteria. So your biological filter is “fairly” safe.

The reason that some tanks experience an ammonia peak after treatment with erythromycin is (probably) not because the biological filter is non-functional. It is more likely that it is because of the high content of protein released from the dead blue-green bacteria which is broken down to ammonia and/or nitrite by the “good” nitrifying bacteria in your biofilter. This boost of protein to be broken down upsets the finely tuned balance of different bacteria in your filter. (Actually, if you killed of all bacteria in your tank and filter, you would never get ammonia).

In many countries in Europe there are restrictions on buying antibiotics. You usually need a prescription. I suggest contacting a vet. If he can prescribe antibiotics for a mouse I’m sure he can do the same for your tank. Remember, your tank is infected.

WHAT NOT TO DO.

First a few things NOT to do (my own, very personal, experience).

If you have an established infection, do not try to get rid of it by turning the lights of. Most likely this will get you into more trouble. Your going to kill of the “good” algae and the plants, but the blue-green bacteria is going to return when you turn the lights back on (usually more fiercly than before).

Personally I don’t like copper. Copper is poisonous to everything - plants, fish, and bacteria. At least in Europe, most “miracle” treatments you buy contains copper.

You could try manually removing the blue-green algae, combined with extensive water changes. But in my experience it’s fruitless, unless you spend all your free time with your fingers in the green slime. Ever tried to clean the stuff away from Cabomba or Java fern? Then you know what I mean.

WHAT TO DO.

Of course, tank hygien is important. Regular water changes and all that. But for those who has been doing it all according to the textbook and still wondering if your doing something wrong, don’t despair, you have’nt been hit by a blue-green curse.

Me myself, I get an infestation in about every second tank (freshwater) I set up. These does not correlate to any increase in ammonia, nitrite, or nitrate (I do not keep check on phosphate, but I plan to). One exception is tanks with soft and acid water. You rarely find blue-green bacteria in these tanks since most bacteria, including blue-green, do not like acid conditions.

The followin is my suggestion for battleing blue-green algae:

First make sure that it is blue-green bacteria and not the “normal” algae. Remember that erythromycin is ineffective on anything but bacteria.

Day 1.

Add 2.5 mg/L erythromycin. If you have a protein skimmer, turn it off. I believe it will inactive a lot of the antibiotic through coprecipitation with protein. It will, however, be very usefull later.

Day 2.

Add 2.5 mg/L erythromycin.

Day 3.

Now you should see a lot of dead blue-green bacteria floating around in the tank. Increase filtration (a second mechanical filter if possible) to get rid of it. If you have a protein skimmer, turn it on. The critical thing now is to get rid of as much protein (dead bacteria) as possible to avoid a peak of ammonia.

Day 4.

Most blue-green bacteria should be dead by now. Try to clean out as much as possible of the dead stuff. I use a jet stream of water from the outlet of a canister filter to remove it from plants and decorations. Combined with the second mechanical filter, this works fine for me. Let the filter work for a couple of hours then make a 50% water change. Add 2.5 mg/L erythromycin.

Day 5-7.

Wash the mechanical filter at least once a day. Keep check on ammonia and nitrite but do not change any water unless absolutely necessary. The extra filter can be removed as soon as the water clears up.

Day 8.

Make a 30% water change. Add 1 mg/L erythromycin.

From now on, resume your normal maintenance.

The concentration I use is in theory a bit high and getting up where it should starts having an effect also on G(- ) bacteria. When I started using erythromycin I had problems using lower concentrations in the tank. It was not very effective. It might be time to check it again.

One word of caution. Only use erythromycin when you really need it or you might end up with blue-green bacteria resistent to the antibiotic.

My practical experience of using erythromycin to battle blue-green bacteria is limited to my own few tank (and some friends). It would be interesting to get some feedback from people with experience (good or bad) of battling blue- green bacteria (with or whithout erythromycin). I would of course post a summary of the response.

Submitted by Ron Reisdorf

Light is the all-important source of energy used by plants in photosynthesis. But light is not just one simple, well-defined entity. The plant response is influenced by light quality, intensity and duration.

The energy contained in light is absorbed in the chlorophyll of plants. Not all wavelengths of light are utilized with equal efficiency. Looking at a chlorophyll/light absorption curve, one can deduce that red and blue light are more effective than green. This is logical. Plants do not use all of the green light. They reflect it. This is why plants appear green.

When electric light sources produce light, the wavelength (color) is determined by many things. For instance, a tungsten filament in an incandescent bulb emits more light with long wavelengths (the reds) when it is relatively cool and more short wavelengths (the blues) when it is very hot.

Other sources emit light in special ways. Metallic vapor lamps are quite efficient for high intensity lighting on larger areas. Fluorescent tubes are the most economical and convenient in limited areas. In the fluorescent tube, special phosphors become excited as electricity is supplied to them and give off energy in certain wavelengths. It is possible to design these tubes to emit primarily red, green, yellow or the “color” of your choice. Not all are equally efficient, but this would appear to have a practical application, since plants do not use all wavelengths with equal efficiency.

To achieve better efficiency in the response of plants to fluorescent light, special tubes have been designed which emit proportionately more blue and red wavelengths of light. In doing so, the green-yellow-orange fraction has been reduced. The loss in this portion of the spectrum, even though it is slightly efficient has not been compensated by enough increase in the blue-red portion of the spectrum to result in increased plant growth.

Critical experiments show that maximum growth of most plants under cool white fluorescent lights will be equivalent to or better than that obtained under the blue-red phosphors. Work by V. A. Helson, Canada Department of Agriculture, Ottawa; and J. W. Bartok and R. A. Ashley, University of Connecticut, indicate that there is no advantage to the use of blue-red fluorescent tubes except for aesthetic purposes. Some of the names of these special tubes are Grolux, Plant-Gro, Plant Light, Vita Light and Optima. The higher cost of these fluorescent tubes may be justified on experimental or aesthetic grounds but is hardly warranted on the basis of plant growth.

Did you know that the recommended amount of light for a planted tank is 7000 - 15000 LUX. Oh LUX is Lumens per square meter. Do you know how many Lumens your bulbs put out? Well most of us do not but if you are here is a more detailed link, and one more. But really most of us do not think about it in LUX as much as the old rule 1.5 to 4 watts per gal. And boy, that too is a large range for determining the right amount of light. Which one do you choose? Well it depends on a few things, like what type of plants you have, and this site can help you there(towards the end). Another consideration is this the depth of the tank and as you may have noticed LUX is sq meters and doesn’t consider depth. A third thing is the spectrum of the bulb you use, plants want blue and red light the rest is almost extra and algae really do not care. Also how far above the tank are your lights. For standard florescent bulbs you want to get them as close as possible. So the bottom line is there is no one answer to the lighting question as with many of the variables in the hobby. The right amount of light depends on a lot of factors one of which can be how fast do you want your plants to grow.

by Wayne Vandre, Horticulture Specialist
(from The CassiDietsch Zoo Fish Page, http://www.users.voicenet.com/~dietsch/fish.html, Jeff Dietsch)