First tank - SOS Algae!

Hello everyone,

I am seeking advice for my 47-gallon (180 liter) planted aquarium that I set up in January. After a month-long nitrogen cycle, I introduced the fish and everything was going well. However, two to three months later, I started to get green filamentous algae everywhere: on the glass, decorations, and plants. I can clean the glass, but the decorations and plants are completely covered.

For the past month, in addition to the green algae, I suspect I now have some Black Beard Algae (BBA) as well. I'm not 100% certain, but it appears bushy and black. My aquarium has become very unsightly with all these algae. I do a 20% water change per week, and the parameters are as follows:

• NO2: 0,20 mg/L
• NO3: 15 mg/L
• pH: 7
• GH: > 4 dH
• CO2: 30 mg/L

The lighting is provided by LED Day 9000 K and 1 LED Nature 6500 K tube for 10 hours per day. My filter is a Juwel Bioflow.

Do you have any advice on how to get rid of these algae?This is my first tank, so I am open to any advice. I have read that overfeeding is also one of the causes, but I admit that I have no idea if I am feeding my fish too much or not. How can I make this calculation?Should I replace all the plants in my tank?

Thank you in advance for your answers!

What a lovely case of black beard algae

Are you adding plant fertiliser and carbon dioxide (CO2) to the aquarium?
If yes, what type of fertiliser and how often?

Do you gravel clean the substrate when you do a water change?

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What is the ammonia level?
How often do you clean the filter and how do you clean it?

You have a nitrite level and you shouldn't if the filter is established. You want ammonia and nitrite on 0ppm (0mg/L) at all times.

You want nitrate as close to 0ppm and less than 20pmm at all times. Your nitrate is 15ppm and is fine but you have a low nitrite reading, which is not normal.

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Algae grows from an imbalance between light, nutrients and live plants. If you have too many nutrients, or too much light, or not enough live plants to use the nutrients and light, you get algae problems. You have plenty of plants so that leaves light and nutrients as the cause of the algae.

Have both light units set to 6500K. Having one light unit at 9000K is adding too much blue light and that can encourage algae.

Do a bigger water change each week and gravel clean any open areas of substrate. Leave about 2 inches of undisturbed substrate around the base of the plants but try to gravel clean the rest of the tank. I recommend a 75% water change and gravel clean every week. This is especially important if you are adding plant fertilisers because it helps to dilute any un-used fertiliser and reduces the chance of you overdosing and poisoning the fish. And if you have an imbalance in the fertiliser (eg: too much nitrogen and not enough trace elements), the plants don't do as well and you can have algae problems.

Turn the CO2 off or down for a month and see if that helps. There is plenty of CO2 in the water from the filter bacteria and fish that produce it continuously. Whilst CO2 is a nutrient the plants need, too much can cause problems.

Do not chuck the plants out, they can be saved. It will take several weeks before you notice any change in the algae. You need to try the things above and monitor for a bit and see how it goes. Some shrimp will eat black beard algae and they also pick up uneaten food, assuming there is any. You can try adding shrimp in a few weeks if things haven't changed but normally when the nutrients and light are correct, the algae dies back. It doesn't always go completely and black beard algae is the worse type of algae, but it can be fixed. Green filamentous algae grows from excess light and nutrients.

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As for feeding, you feed the fish as much as they can eat in a couple of minutes and then remove uneaten food. The best way to do this is to offer a small amount of food and let the fish eat it, then add a little bit more. Continue doing this until the fish are no longer racing in and eating all the food instantly, then stop feeding.

I don't think overfeeding is causing this. It is more likely to be plant fertiliser and incorrect lighting.

Hi Colin_T,

Thank you so much for your incredibly helpful post—I really appreciate it.

To answer your questions:

1. I do not use CO2 nor plant fertilizer, so I don't think the problem comes from there.

2. When I do water changes, it's true I don't gravel clean the substrate enough. I have very thin substrate (sand), and when I try to gravel clean, I end up vacuuming lots of sand. Do you have any tips on how to do this correctly? Should I consider changing it completely and using a larger grain substrate to prevent it from being vacuumed?

3. I never measure the ammonia level. Do you think I should buy a kit to test it? Does ammonia influence the algae problem in this case?

4. Concerning the nitrite levels, am I not bound to get some reading fluctuations? My fish are generally small (guppies, cardinals, corydoras, and gastromyzon), but I do have two celestial goldfish that produce a lot of waste. Should I expect nitrite fluctuations because of them?

5. I also have shrimp that are constantly fussing over the substrate.

6. I have a Juwel Bioflow filter with all the corresponding sponges, and I change them according to the manufacturer's recommendations.The first one (purely mechanical, I change it several times per week). The Bioflow filter system includes the following sponges:

- **Coarse Sponge**:
- **Fine Sponge**:
- **Nitrate Sponge**: .
- **Carbon Sponge**:


7. Concerning water changes, I'm unable to do more than 20%. The water hardness where I live is extremely high, and I can't use it directly in the tank. I'm producing osmosis water for my weekly changes and can't produce more than the quantity I currently do. My tank is far from a water point, and I'm doing my changes with Jerry cans for the used water and others for the osmosis water. Being in a small apartment, I can't store more than the ones I currently have.

8. The lighting used is the one recommended by Juwel. Should I change the 9000K bulb and have two at 6500K? Also, do you think having the lights on for 10 hours a day is overkill?

At this point, my plants are so covered up (even my snails have black algae on their shells) that I'm tempted to move the fish to a smaller tank and change the substrate and plants completely. The decors I was able to clean with bleach.

Thanks again for your help!

2) The pictures show what appears to be gravel on the bottom of the tank. Do you have gravel and sand?

If you kink the syphon hose when gravel cleaning the substrate, it will slow the flow of water down and you shouldn't suck the sand out.

You don't need to change the substrate unless you want to, but the plants look to be healthy apart from being covered in algae.

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3) Ammonia can be a major problem and will certainly encourage algae to grow. Ammonia test kits can be useful when setting up a tank and cycling the filter, and if things go wrong. But outside those times they rarely get used unless a fish dies. However, in this situation, knowing the ammonia level might give us more information. Since you have been changing the filter media, you might have ammonia problems too.

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4) In a healthy biological filter you shouldn't have any ammonia or nitrite readings unless you have just fed the fish in the last 10-15 minutes (30 minutes max). Then you might get a low level reading. But if you haven't fed the fish for an hour or more, then you shouldn't get any ammonia or nitrite readings.

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6) What are the manufacturers instructions on changing the filter media/ materials?

Most filter companies want your money and suggest you replace certain bits of media regularly. This is good for them because they keep selling you stuff. Unfortunately it can stop a biological filter from becoming established because you are constantly removing the beneficial filter bacteria when you replace the piece of filter media. This can cause ammonia and nitrite problems in the water. When companies say you must change this media every x weeks, they are using a sales ploy to take your money.

If you have sponges in a filter, they don't get replaced unless they start to fall apart, which might happen 10+ years after you get them. Sponges are the best type of filtration because they trap gunk and hold beneficial filter bacteria. They are cleaned once a month by squeezing them out in a bucket of aquarium water. The sponge is re-used in the filter and the bucket of dirty water goes outside on the lawn. The rest of the filter case and impeller assembly can be washed under tap water.

If you have carbon (black granules) in the filter, this can be left out of the filter because it isn't necessary unless you are trying to remove chemicals or heavy metals from the water. If you do have carbon in the filter, it should be replaced about once a month but I don't recommend using it unless you are trying to remove chemicals or heavy metals from the water. You can replace the carbon with another sponge. You should have a carbon filter in the reverse osmosis unit that you use.

I'm not sure what's in the nitrate sponge but that type of filter media usually removes nitrates from water. Water changes do exactly the same thing. If you want to use a nitrate sponge, that is up to you. Personally I think they are a rip off and waste of money unless you have nitrates in the tap water. Then you should filter the tap water before using it in the aquarium. You are using a reverse osmosis unit to make water for the fish tank and that should be removing nitrates from the tap water, so you don't really need a nitrate sponge. I would replace it with a normal sponge.

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7) Guppies and goldfish don't mind hard water (200ppm/ 11dGH) but the tetras and Corydoras like soft water (less than 100ppm/ 5.5dGH). Ideally you would have 2 tanks, one for goldfish and guppies, the other for the tetras and catfish. The GH is not too bad but you can't really raise it without adversely affecting the softwater fishes (tetras, Cories).

Is there any way at all you can store more filtered water to do a bigger water change?
If not you will have to stay with the 20%, but bigger water changes are generally better because you remove nutrients.

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8) Do you have LED light units or fluorescent lights?
If you have globes and not LEDs, and you can change the 9000K globe to a 6500K globe, that would be better. You could try running one globe only (the 6500K) and see if it helps but it might not.

Having the lights on for 10 hours a day is normally fine. I used to run my lights for 16 hours a day and never had algae problems. If you want to reduce the lighting time, try running the single globe first for a month and see what happens. If there's no reduction in algae, then try reducing the lighting time by an hour a day. Run it at 9 hours a day for a few weeks to a month and see how it goes. Don't do both at the same time though.

Juwel tanks nowadays come with two LED tubes, one at 6500K and one at 9000K. They have fixed output so the only option would be to buy a second 6500K LED and swap out the 9000K tube.

Juwel filter media:
Black sponge has carbon impregnated in the sponge. Carbon is not needed routinely, the best thing to o=do with it is leave it in the cupboard to remove medication after treatment if the fish ever get sick.
Green sponge is supposed to remove nitrate but the general consensus is that it doesn't. Best thing with this is pretend it's a blue sponge.
White pad is filter wool/floss. It's first in the direction of water flow to catch bits so it clogs quickly. It won't wash properly as it goes shapeless and holey so needs replacing frequently. It is cheaper to buy a length of filter floss from a roll and cut it to shape.

Juwel says to "clean or replace the coarse sponges every 6 - 12 weeks and fine sponges every 3 - 9 months". Sponges need cleaning in tank water taken out at a water change more often than that and should only be replaced when they fall apart. They'll last for years.



I would cut the light duration down to 6 or 7 hours (though if Colin says different, do what he says) and see how the plants are after a couple of weeks. If they appear to be suffering, increase by one hour and see how the plants cope.

Sammu89 said:

LED Day 9000 K

Click to expand...

This is the main cause of the algae. You will not solve the algae problem until you alter this bulb. Change it for another nature bulb at 6500k or turn the bulb over so the opaque side is facing down (don't open the lid with the light on like this though, you'll hurt your eyes).

Essjay said:

Juwel tanks nowadays come with two LED tubes, one at 6500K and one at 9000K. They have fixed output so the only option would be to buy a second 6500K LED and swap out the 9000K tube.

Juwel filter media:
Black sponge has carbon impregnated in the sponge. Carbon is not needed routinely, the best thing to o=do with it is leave it in the cupboard to remove medication after treatment if the fish ever get sick.
Green sponge is supposed to remove nitrate but the general consensus is that it doesn't. Best thing with this is pretend it's a blue sponge.
White pad is filter wool/floss. It's first in the direction of water flow to catch bits so it clogs quickly. It won't wash properly as it goes shapeless and holey so needs replacing frequently. It is cheaper to but a length of filter floss from a roll and cut it to shape.

Juwel says to "clean or replace the coarse sponges every 6 - 12 weeks and fine sponges every 3 - 9 months". Sponges need cleaning in tank water taken out at a water change more often than that and should only be replaced when they fall apart. They'll last for years.



I would cut the light duration down to 6 or 7 hours (though if Colin says different, do what he says) and see how the plants are after a couple of weeks. If they appear to be suffering, increase by one hour and see how the plants cope.

Click to expand...

Can he run the jewel tank with just one tube? He clearly has too much light so replacing the 9k with another 65k is probably not needed. BBA is a different beast and i can't help there (I have a bit of it myself when i transitiion from tap to ro in one aquarium); but most algae issue are too much light. Yes there is an imbalance and reducing fertilizer will help but the first thing to do is reduce light. People over-estimate how much light most simple plants require.

Unfortunately Juwel lights won't work unless there are two fully functional tubes in place.