# What to do when bluegreen algae take the lead



## harrykaa (Jan 10, 2005)

What can you do when Cyanobacteria (bluegreen algae) take lead?

Is this familiar to you?
1. Very persistently, dark green or bluegreen mat appears on the sand/gravel, on the rocks, on the wood and also on the plant leaves.
2. You are relieved at the ease this weak mat can be removed and siphoned off. Also by gently rubbing you are able to remove it from the plant leaves.
3. After cleaning only few hours have elapse and you notice signs of the mat forming again. The next day it has recovered fully. If you do not remove it, the mat will cover everything in your tank.

This is bluegreen algae (BGA). They are actually bacteria, which are capable of photosynthesis. They are unicellular or filamentous. Scientists claim that they are in-between organisms with bacteria and algae. They can grow extremely rapidly and form large beds in the water. During this bloom many species (like Anabaena, Nodularia) also produce toxins (hepatotoxin) into the water.

*Algicids*
I have come across articles where algicids (like CuSO4, monouron, diuron, simazin) have been tried with a consequence that true algae has died, but not BGA; or it has come back immediately after treatment. I do not recommend algicids, because chances are this is also the way to eventually kill almost all the higher plants in your aquarium.

Algicids usually trigger into photosynthesis. The theory is that in small amounts the more delicate and simpler algae suffer the most. They usually do, but remember that algae can also grow back and recover faster than higher plants. Thus the problem may even become worse after the treatment. Usually algicids stop photosynthetic activity of all plants for the duration of medication. Higher plants will suffer if the medication is prolonged or restarted.

The only right way to use algicids is that you simply first remove your higher plants from the tank and only then put the medicine in. After the algae have died, you must remove it. This is important, because no algicid can make algae disappear. After the treatment you just have millions of dead bodies lying everywhere in your tank. When bacteria break them down, you have the best fertilization for the new algae generation to build up. This is a temporary remedy. It does not remove the cause for algae bloom in the first place.

*Antibiotics*
As the BGA are bacteria, they can be treated with antibiotics. In fact, BGA are sensitive to many antibiotics. Bacteria can be divided (Gram staining technique) into gram-positive (+) and gram-negative (-) bacteria. Widely used Erythromycin will kill gram-positive (+) bacteria and also sensitive gram-negative (-) bacteria, like Cyanobacteria (BGA). The problem here may still be that important freshwater nitrogen cycle bacteria (Nitrosomonas, Nitrobacter) are also somewhat sensitive to Erythromycin. This may lead to the need to recycle the tank water if you overdose antibiotics. After treatment the tank water can experience an ammonia peak. This is due to the protein of dead BGA broken down. So you must remove the dead algae to avoid it.

Anyway after a medicine treatment, where some bacteria have died, your tank water is in an imbalanced state.

*Biological method*
This involves three different measures that have to be combined. These will, however, bring about a durable long term solution.

_1) Persistent cleaning + adding plants_
As the BGA is usually mechanically easy to remove (wiping the plant leaves, siphoning gravel), you do not need to kill it before this removal. The removal is obligatory anyway. So keep cleaning as often as possible. At the same time small amounts of water is changed.

Plants use up nutrients like nitrates and phosphates. In order to grow well plants need also adequate amount of light (species dependent) and carbon dioxide (CO2). If you use a strong light (usually 2 or more watts per gallon), you must provide for the plants extra carbon dioxide.

_2) Cutting down the input of bio load_
The bluegreen algae bloom in nature (in the lakes and the seas) because phosphates (PO4) are present. BGA bloom need also nitrates and they are usually sky high when bloom occurs. But some BGA can also with the presence of phosphates fix atmospheric nitrogen when nitrates levels are low in the water. In nature where bottom sediments contain great amounts of phosphates, these will dissolve into water column only when adequate level of oxygen is present. In aquarium the situation is slightly different. The sediments do not exist and there is always enough oxygen.

If you have only some common decorative fishes in your tank, it is easy to cut down the feedings and thus control the input of bio loads. But on the other hand, especially if you have a shoal of Pygos or a big hungry Rhom, it is almost impossible to fully control this input. The situation is even worse when we talk about overcrowding. You can, though, feed the kind of food that does not break into million peaces during feeding frenzy. There is a great difference feeding them a living rat or a fresh and firm fish fillet.

When using fertilizers be careful not to use those that contain nitrates or phosphates. Usually only iron (Fe) and maybe manganese (Mn) and magnesium (Mg) are important. The fishes will provide the rest for your plants.

_3) Effective bio filtration + regular water changes_
Without filtration and water changes your tank will end up being a poisonous waste box.

In order to have an effective bio filtration (canister filter or a wet-dry sump) it has to be large enough and the water circulation has to be big enough to provide oxygen for nitrogen cycle bacteria. The canister filter will also function as a good mechanical filter. The most important thing here is the volume of the bio filter mass. Providing excess water circulation does not improve the efficiency. At a certain point it will even hamper bacterial growth and nutrient absorption.

Regular water changes are a must. Even if you have a fully working bio filtration, you can end up having too much nitrogen in your water. In a piranha tank the load input is always too big for the plants to use up. Also with regular water changes you can remove surplus phosphates, detrimental bacteria, decaying material etc.

A good water balance is important in fighting the BGA. Watch the nitrate and phosphate levels. Less light is not an answer. That way only the higher plants will suffer. Although direct sunlight must be avoided. Also high pH will help BGA to grow. The BGA do not like even slightly acid conditions. Remember that usually big water changes (tap water) tend to raise the pH.

Please feel free to reply to this thread for comment but also for discussion on your BGA problems.

Regards,


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## elTwitcho (Jun 22, 2004)

Fantastically written article, but I have to strongly disagree with you on this point;



harrykaa said:


> _2) Cutting down the input of bio load_
> The bluegreen algae bloom in nature (in the lakes and the seas) because phosphates (PO4) are present. *BGA bloom need also nitrates and they are usually sky high when bloom occurs.* But some BGA can also with the presence of phosphates fix atmospheric nitrogen when nitrates levels are low in the water.[snapback]1135541[/snapback]​


I find this to be exactly the opposite in reality. The best method for combatting any form of algae is to have the plants outcompete the algea. BGA usually takes hold because of a LACK of nitrates in the water, not an excess. With a lack of nitrates but other nutrients being present, your plants become unable to use up the rest of the nutrients present in the water column, while the BGA is able to derive nitrogen from atmospheric gas and therefore has an advantage over the plants. This is all too common when nitrate levels are at 0 and the most obvious cure is to *add* nitrates to the water column so that your plants can take up the rest of the nutrients. If you get a BGA outbreak with high nitrates, there is another issue contributing to your algae problem than nutrient balance, either that you don't have enough plants to absorb the nutrients or your light and CO2 levels are insufficient to allow the plants to uptake the nutrients in the water column.

Otherwise I think it's excellent.


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## harrykaa (Jan 10, 2005)

elTwitcho said:


> Fantastically written article, but I have to strongly disagree with you on this point;
> 
> I find this to be exactly the opposite in reality. The best method for combatting any form of algae is to have the plants outcompete the algea. BGA usually takes hold because of a LACK of nitrates in the water, not an excess. With a lack of nitrates but other nutrients being present, your plants become unable to use up the rest of the nutrients present in the water column, while the BGA is able to derive nitrogen from atmospheric gas and therefore has an advantage over the plants. This is all too common when nitrate levels are at 0 and the most obvious cure is to *add* nitrates to the water column so that your plants can take up the rest of the nutrients. If you get a BGA outbreak with high nitrates, there is another issue contributing to your algae problem than nutrient balance, either that you don't have enough plants to absorb the nutrients or your light and CO2 levels are insufficient to allow the plants to uptake the nutrients in the water column.
> 
> ...


elTwitcho,

You are right in that particular situation in aquariums, where BGA can grow even in a low nitrate concentrations. However, not all BGA species are capable of atmospheris nitrogen fixation (Nodularia etc. is).

Anyway what I was trying to express, is that BGA still needs nitrogen from water (usually it is nitrates in nature) or by atmospheric fixation in case of some species. BGA do not need excess of nitrogen, it need excess of phosphates. So I assume we can agree on this.

I did write this because in my home country (Finland) our sea, The Baltic Sea, and especially the Finnish Archipelago and the Gulf of Finland are still very burdened and eutrophic. Its sediments contain huge amounts of phosphates among other things. The bluegreen algae bloom are common here every year: immediately after the winter and then in the midsummer.

Yes of course BGA is combatting with true algae and higher plants and some BGA species have the advantage to grow in low nitrogen concentrations which true algae do not.

I did not emphasize the fact that in an aquarium higher plants are able to starve BGA (and true algae too) by using up phosphates if other conditions are met (like light, CO2, Fe, Mn, Mg). This is a delicate balance that I have not been able to accomplish. I know you have, though.

Please you can read more indepth study about Nodularia in the Baltic Sea from this link. It says:
_"The substantial input of nitrogen and phosphorus compounds from
municipal and industrial wastes as well as from agriculture promotes the
growth of phytoplanktonic organisms, which are the most frequently used
indicators of eutrophication."_

Institute of Oceanology, Gdynia, Poland

Regards,


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## elTwitcho (Jun 22, 2004)

First of all, excellent discussion harry, I'm glad you started this.



harrykaa said:


> Anyway what I was trying to express, is that BGA still needs nitrogen from water (usually it is nitrates in nature) or by atmospheric fixation in case of some species. BGA do not need excess of nitrogen, *it need excess of phosphates. So I assume we can agree on this.*[snapback]1135612[/snapback]​


I agree with you absolutely, and therein lies my point. I'm a believer in using plants to suck up phosphates so that the algae doesn't get them, and though I haven't experimented much with a light plantload, I believe this can be attained by keeping phosphate levels down through rigorous cleaning pactices. However, in a situation where you have more nitrates than phosphates, the plants will run out of phosphates for growth before they run out of nitrates, and in this case you will rarely see any significant amounts of algae develop (in my experience that is). If however, there is an insufficient amount of nitrates, when the nitrates are gone the plants stop sucking up phosphates, and you are left with phosphates in the water that the plants can not use. The BGA however, is not so limmited by nitrate levels however, and in the absence of nitrate can use atmospheric nitrogen to suck up the phosphates. Yes it is an excess of *unused* phosphates that leads to most algae outbreaks, but I feel that in most cases of BGA outbreak it is a shortage of nitrates that allows that unused phosphate to build up, not an excess of nitrates.

Granted though, I do agree that if your tank is just plain dirty there will be a point where there are more than enough phosphates AND nitrates for the algae and the plants to get all they want, but in that case it's an issue of poor tank maintenance, not necessarily nutrient balances.



harrykaa said:


> Please you can read more indepth study about Nodularia in the Baltic Sea from this link. It says:
> _"The substantial input of nitrogen and phosphorus compounds from
> municipal and industrial wastes as well as from agriculture promotes the
> growth of phytoplanktonic organisms, which are the most frequently used
> ...


Good link, it's certainly an interesting bit of information. I do believe however that the situation being seen in the baltic is one that is comparable to what would happen with bad tank maintenance in an aquarium. The amount of nitrates and phosphates is so high that it simply overloads the systems ability to cope and you have BGA blooms. However, I think with most responsible aquarists running a planted tank they would not be seeing situations such as these because there should not be enough decaying bio matter to produce such excesses. I would think that in almost all circumstances where an aquarist who is devoting some amount of effort to tank upkeep gets a BGA outbreak, it is a shortage of nitrates relative to phosphates that is causing the bloom, not an excess of nitrates.

Very interesting discussion though, thank you for starting this


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## harrykaa (Jan 10, 2005)

elTwitcho said:


> First of all, excellent discussion harry, I'm glad you started this.


elTwitcho,

Likewise, thanks for your valuable replies. I agree with you.

Regards,


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