Eradicating algea from planted aquarium

Fighting with algae is not always an easy task. However if you know how to deal with them it is much easier to keep them under control. The key is to hit the cause of algae, find a balance and keep the routine. Main causes of algae in planted aquarium are:

  1. Too strong light intensity and lighting period or improper spectrum
  2. Not enough water changes (higher amount of organic compounds and nitrates in the tank)
  3. Too much aquasoil which leeches organics and breaks out too quick, especially with co2, releasing too much organics to the water (needs more water changes)
  4. Over fertilizing with micro elements and macro elements NPK (nitrogen, phosphorus and potassium)
  5. Not enough plant mass and stunned or slowed plants growth
  6. New not fully established aquarium
  7. Not enough filtration or water flow
  8. Fluctuating co2 levels
  9. I neglected my aquarium for too long

Too strong light intensity and lighting period or improper spectrum

Light plays the main role in planted aquarium. Especially when fighting with algae. It is crucial to choose a good light from the beginning depending on your plants needs and setup. Without adding co2 into the water column plant growth is much slower than if the co2 would be delivered in proper amount, usually around 30ppm. The best light for planted aquarium will have a peak and be most efficient in the middle of blue and red spectrum. Plants mostly reflect the green light spectrum but it is needed for a better look.

That is why the easiest light to grow plants will be a full spectrum daylight usually around 6500-6800 kelvins. This tells you mostly only about the light color, but usually this kind of light will have its peaks in the most needed wave lengths. More about the aquarium lights.

‘In most plants, photosynthesis occurs in special cells known as chloroplasts. The green color we see in plants is caused by small grains of green light absorbing pigment inside the chloroplasts. These pigments name is a chlorophyll (chloro=green; phyll=leaf).

Many different types of plants use different kinds of chlorophyll during photosynthesis. Chlorophyll a is the pigment directly responsible for transforming light energy (sunlight) into chemical energy (carbohydrates). Many plants also contain chlorophyll b and chlorophyll c, pigments which help carry out other chemical processes.’

Sometimes it is interesting defense ability of the plants to utilize different kind of lights. Red plants reflects red light which is very important to proper plants growth. That is why they need a stronger light. They use to grow in strong light environment in nature that is why they became red. Some plants can change its color, being green with weaker light and changing red, pink or purple when more light is delivered. Let’s focus on algae.

You have a proper light intensity for your aquarium setup. How long should you run the light for to avoid algae? In new setup less light is needed and I recommend starting lower light intensity. Tropical plants needs longer lights period around 11-12 hours a day. Some people does even 14 hours. However I would recommend with shorter light period on the beginning, because right after planting your plants they will start developing roots and getting use to new conditions. It may take up to 3 weeks so running your light at 7-8h a day should save you a problems with algae on the beginning. Then gradually stretching it as everything goes well.

Some kind of algae like diatoms are hard to avoid, because they usually appear in new setups due to improper biological balance. It will go away over time, but lowering lighting time will for sure help you overcome this issue.

Not enough water changes (higher amount of organic compounds and nitrates in the tank)

Depends on your setup it is recommended to do a 50% of water change every week, and keeping this routine. Doing it in the same day will give the plants stability and routine they need and help you fighting with algae. Plants like people needs some kind of stability in life to grow. When everything is changing often is hard to settle down.

If you used aquasoil or regular soil it will leach ammonia depends of kind of aquasoil or soil, substrate thickness and size of the aquarium. Soil usually leeches ammonia for the first 2-3 weeks. It helps with cycling your tank as it delivers food source for your beneficial bacteria to grow. If your ammonia level doesn’t rise over 0.25 you don’t have to do more frequent water changes. Once a week is just fine. However with aquasoil like ada amazonia high in ammonia, it is needed to do a daily water changes for the first 7-10 days depending on ammonia levels to avoid algae growth. Later on you could go down to two 50% water changes a week and when everything is getting more stable, plants growth is good and algae doesn’t out compete plants, you can go down to one 50% water change a week.

It is always better to do slightly more than 50% of water change than less than that. It is also connected with fertilizer build up but about this in a moment.

Keep your nitrates at the orange color which is lower than 40ppm. You need to test them at least before and after water change in order to know what is going on in the aquarium. If nitrates build up is too fast and one water change is not enough to remove this accumulation, you will have to do another water change in 2-3 days, with total 2 water changes in a week.

Innert substrates like eco-complete are much easier and it needs much less water changes from the beginning.

Too much aquasoil which leeches organics and breaks out too quick

With regular soil it is recommended to add only 1 inch, but it is not a golden rule. You can add much more than that, especially when it is capped properly. It is better to mineralize your soil a little which breaks your soil and speeds up the break down process. It is important to sift the soil and remove all the cork and dry weeds or pieces of wood before you add it to aquarium. Otherwise those elements will break down and will pollute your water for a longer time. If you don’t mineralize your soil, remember to poke the soil daily as it will release gasses during the break down and may cause pockets which will ‘blow up’ and make your water dirty.

With aquasoil it is a little easier task, just keep your water changes routine and it will be fine. In my opinion it is better to add less soil than too much, depending on the kind of plants you wanna keep. It is usually enough to keep 3-4 inches of substrate in your aquarium. It gives plenty of space for roots to grow. If you wanna build higher peaks or mountains you can always use something else like lava rock or power soil, as well as regular rocks on the bottom to add the height.

Over fertilizing with micro elements and macro elements NPK (nitrogen, phosphorus and potassium)

In my opinion it is the most common mistake right after improper lighting which causes algae blooms. Just adding too much microelements should not promote algae growth right away. It is fertilizer build up which causes that, due to not enough water changes. If you are dosing full Estimated Index method which is adding much more fertilizer than plants need. This fertilizer will build up if you won’t do 50% of water change every week. You do not have to dose whole NPK right away, until plant will grow roots and settle down. Just potassium is fine.

Usually people read the description on the fertilizer and dose according to this which is a huge mistake! They do not take to consideration their aquarium conditions, plant mass and aquarium age. I recommend starting with as low as 1/4 1/3 recommended dosage. This way plants will get use to stable access to nutrients and will start growing fast and need more nutrients. People most likely add too much and experience algae than see plants deficiencies.

Some when starting their adventure with planted aquarium wants to ‘breed’ plants (grow them as fast as possible), but everything have its time. Full dosage should take place after 2-3 months of having a tank growing with plants and fast growing species taking over at least half of the whole aquarium capacity.

Not enough plant mass and stunned or slowed plants growth promotes algae growth

Not everybody have fortune right away to buy enough plants for their aquarium. People like me started slowly with growing plants trimming and replanting. In my opinion what is very helpful is keeping 2-3 kinds of very fast growing plant species from the beginning, even though those are not the plants you wanna keep in that tank and you will have to remove it later.

Those fast growing plants species like hygrophila species will help you out fighting with algae right from the start. It may came out that you will like them a lot or you can sell some of the trimmings to your friends.

When plants growth is stunned or slowed down, remember to lower dosage of the fertilizers you add. Try matching it with their needs. This is the moment when most likely you will experience algae, lowering your light intensity if possible (dimming it) or lifting it 4 inches higher above the tank should help a lot. Also lower light period to 7-8h. In my opinion it is much better to lower the light intensity in this case than lighting period first. Or lower it just 1h. Find your way observe the plants, they are the answer. Not every setup is the same and there is not such a thing like one answer. Expect different opinions but drag your own conclusions from it and research with your own experience.

New not fully established aquarium

It is called new tank syndrome. Biological balance is not yet achieved so all the processes will go slower. Plants won’t have enough nitrogen coming from breaking down organics by their roots. With innert substrate it is easy, dose NPK smaller amounts 1/4 from the beginning. Aquasoil needs much more time, up to 3 weeks. You may add some of the established substrate on the bottom of your tank right when you are setting up your aquarium, established filter from other aquarium or some filter media from it to your new filter. Just remember to provide food source for your bacteria if you are using innert substrate. It might be some fish food or a little bit of water from another aquarium. I do not recommend adding a hardy fish to your tank at that time. They will suffer and become weak and might get some disease easier. With aquasoil you don’t have to add anything, it leaches ammonia which is a perfect food source for your beneficial bacteria to grow.

Not enough filtration or water flow Algae appears in some spots

You can keep your aquarium with just a bigger sponge and air pump plugged in to it as an aquarium filters. Planted aquariums needs some more water flow so you could add a power head to improve circulation. For smaller aquariums hang on back filter is just fine (HOB). I recommend aquaclear brand myself even though sometimes I have a problem with starting it after water change. For bigger aquariums I truly recommend a canister filter, which has a good water flow and lots of space for a filter media. It is good to adjust it to your needs by adding better filter media than those you purchased with the filter. 

It is good goal to have 10x more water filtration than the size of your tank, but you could go with a lower turnout. You could have even more as long as you don’t use any ‘chemical media’ like special phosphates or ammonia removers or charcoal. I do recommend adding a bag of purigen to your filter media.


Fluctuating co2 levels

When you are adding co2 into your aquarium it is crucial to maintain the same amount of co2 drops all the time. Target level of co2 in your aquarium should be 30ppm(see ph/kh chart to read how much co2 is in your tank). If co2 is stable you will avoid fluctuations and algae. Second thing is how you deliver co2 into your aquarium and distribute it. If you don’t have glass diffuser, reactor or inline co2, most likely you will have bba algae in the spots of fast water flow. For example if your co2 is plugged to a power head then in the spots where it shoots co2 together with the flow you will have algae, no matter how perfect conditions you have in your aquarium.

In order to maintain stable level of co2 during the lights on, it is always good to start adding co2 into your aquarium around 1hour before the lights are on(specifically as much earlier as it takes to drop ph till the level when there is 30ppm of co2 in the water). This way when the lights are on, plants have ready and available co2 levels in the water. If you running co2 together with the lights on a one timer, co2 on the beginning will accumulate much slower to the maximum safe level, because plants will be already using it to photosynthesize.  The curve of how co2 grows to the level of 30 ppm will be longer, because of that. That’s why it is better to start accumulating it before the lights will turn on.

Neglected aquarium

If you didn’t have time to take care of your tank or went out for a weekend or week/two weeks, you may come back to aquarium with algae. There are certain steps which you could do to eradicate algae in your aquarium. 

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