Have a problem with brown alge - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 12 Old 04-06-2012, 10:04 PM Thread Starter
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Have a problem with brown alge

I have been having a problem with brown alge the last 3 or 4 weeks. Does anyone know what causes this and what I can do to get rid of it? I have had fish in my tank since about early feb.

Recently, I had one snail die (I had 3, now down to two). Also, my Molly is acting very lethargic--mostly sitting on the bottom. Could these have anything to do with the alge? Or my vacuuming of the gravel?

My levels are reading the same as they have been since my tank was established. Nothing new there.

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post #2 of 12 Old 04-06-2012, 10:14 PM
What are the levels reading in your tank?

Algae is often seen in newer tanks. It will usually stop growing over time but you will have to find a way to remove what is already there. So you could just be patient and use a algae scrubber or razor to remove it from the glass.

Do you have any live plants in the tank?

Another popular reason algae grows, even in established tanks is because of too much light. If you dont have plants you really dont need much light on the tank at all, few fish like it. Even with plants you only need about 8 hours of good lighting.
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post #3 of 12 Old 04-06-2012, 10:16 PM
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What are the levels. What kit are you using to give you the levels (strips or liguid)?

can you get a photo of the brown algae. Often in new tanks brown diatoms form. It's basiclly a light brown dust that forms on everything and can be quickly wiped off. It's the nature of the new aquarium. It has to do with minerals in the water and it takes time to get it out. BUt it could be something else so here a picture would help.

The molly is sitting on the bottom. Are the rear fins clamped, so instead of looking like a Y it looks like a I?
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post #4 of 12 Old 04-07-2012, 09:43 AM Thread Starter
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I tried attaching pics. Hope it worked?!

My levels (as of this morning) are:

PH 6.6 or 6.8 (the color is close to both--hard to tell)

Amnonia 0.25 Have had trouble getting this to zero. Has been this way for a couple months. I do weekly water changes of 25% (by vaccumming the gravel).

Nitrite 0

Nitrate 0+ This is a question for me. It is not the bright yellow of 0, but it is nowhere near the color of the first numbered reading either. I have been very careful to follow the instructions, but I always get a gold yellow color.

I am using the API drops to test the water.

I also suspect, from your comments, that the brown alge is due to too much lighting. I have been turning it on at about 8:00 am and off at 11:00 pm. Clearly too long. Do the fish mind if you turn it off and on during the day as you are in the room?

Also, I have only fake plants.

I have a 20 gal tank.

My fish are:
7 neon tetras
3 von rio flame tetras
3 emerald cory catfish (I think they are the bigger ones, not the true cories)
1 molly (the one in question)
1 platy (the other died a couple weeks ago, but I don't think it was ever healthy. Have had a lot of trouble with the fish from the LPS, which the platys and molly are).
2 lg and one vey small snail (a third large was the one that died last week).

One last question: I was told at the pet store that aquarium salt was healthy for all tropical fish and to add it when I do a water change. I did add some about a month ago, but since I do water changes every week, I have not wanted to add it every time. Also, I question whether the salt is good for the other fish (other than the platy and molly). Please advise.

Thanks for all the help!
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post #5 of 12 Old 04-07-2012, 10:44 AM
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Well any amount of ammonia is not good. Make water changes more often and about 50%.

That is far to much lighting. You want 7-8 hours. Too much invites algae. If you wish you can make it 2 4hour periods, but don't turn them off and on. Lights in the room do affect them, but as long as there is complete darkness for 8 hours it will be okay.

Lose the salt. Not needed. Useful for medicine.

The live bearers (molly and platy) like hardwater, the tetras like softer more acidic water. The snails also like more hardwater. The acidic water is not good for their shells.
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post #6 of 12 Old 04-07-2012, 11:46 AM
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My comments will pick up on what others have mentioned. First, the brown algae (diatoms) is nothing to worry about, this is common in new tanks (during first 3 months or so). Light actually has nothing to do with this particular issue, but I won't get into that as there are other more significant issues.

First, the molly. This is likely due to the soft water. If the pH is below 7, it is acidic, and usually this goes along with soft water. For more general background info on hardness and pH you can read here:

Livebearers absolutely must have medium hard or harder water, and the pH must be above 7. As you tap water would appear to be the opposite, I would stay with fish that appreciate that: your tetra will thrive, as will almost every fish except for any livebearers. The molly will die, expect it, as ammonia at any level is toxic to this fish and it is already weakened by the stress of the soft water on its physiology. Stay with soft water fish.

Ammonia above zero is trouble, but this is likely due to the newness of the tank and fish issues. Live plants will solve this. I wold suggest floating plants first, they are fast growing and thus use a lot of nutrients, and plants get their nitrogen from ammonia, so they grab it fast. Some Water Sprite is ideal, but many stem plants can be floating. By the way, you see Water Sprite shades, that means this species is in our profiles, so you can click the name to see info on this species. Similarly for Common Molly, Neon Tetra, etc. Profiles are under th second tab from the left in the blue bar at the top of the page.

Salt, never in a freshwater aquarium. Water changes will reduce the salt bit by bit, so please don't add more. You can read what salt does to freshwater fish here:

On the light, when you have live plants (I really do recommend this, nothing helps your tank as much as live plants) an 8 hour day is sufficient. We can discuss tubes/bulbs for your light later, some are better for plants. For plants and fish, a consistent light period is best, so choose when you are normally home to view the fish and have the 8-hour period within that time.

Your 20g is fully stocked with the tetra and catfish, even without the livebearers. If the store will accept the platy back, even for nothing, I would; the molly too, except it is obviously unhealthy and they likely won't take it.

Hope this helps.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #7 of 12 Old 04-07-2012, 12:30 PM Thread Starter
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Thank you all for all your help. I have realized that the molly and platy were now good matches for the others, but unfortunaltely, I realized it after I had them. I never thought to take them back, that is a good suggesetion (especially since it was the store that told me it would be okay in the first place!).

As for the plants, they were suggested to me a by all of you little while ago, so I looked into it. There don't seem to be any stores in my immediate area that carry them (central jersey-north of princeton). Does anyone know a good source to purchase them from?

Thanks again for your advice.
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post #8 of 12 Old 04-07-2012, 12:32 PM Thread Starter
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One last question: If my ph is not good for the snails, can someone recommend a good algae eater as a substitute? I have a 20 gal.
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post #9 of 12 Old 04-07-2012, 03:37 PM
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I think the Otocinclus macrospilus (oto Catfish) would be compatible with your other fish. It eats diatoms and some forms of algae. Most are wild caught so they might be sensitive. Some forms of freshwater shrimp eat algae. If your interested make a post in the invertebrate sub-forum about them.

edit: I was hoping to get a link for the fish profile but didn't. As Bryon said click the second tab near the top for fish profiles. They are under catfish. There is also plant profiles in there too. Might want to read up a bit in case you find a local store.

I do not know what stores you have around you but if you have a petsmart or petco, they both sell plants in tubes. There are a few tricks but they will work. One first trick is to make sure the tube says aquatic plant. If it says semi aquatic or terrarium do not buy it. Second trick is that they are typically grown out of water, but they will survive in the aquarium, what you have to know is that over time the leave will brown and die. But it will grow new leaves. Make sure to trim the old ones as they brown. I suggest a sword, anachris, or wisteria. They are typically the true aquatic for those tubes. Some petcos sell plants in tanks, those have a better selection.

Last edited by TwinDad; 04-07-2012 at 03:42 PM.
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post #10 of 12 Old 04-07-2012, 03:45 PM
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Originally Posted by jcngo View Post
One last question: If my ph is not good for the snails, can someone recommend a good algae eater as a substitute? I have a 20 gal.
The best snails are Malaysian Livebearing Snails. They burrow through the substrate, a great benefit; and they will be fine in any water, soft or hard, unlike some other snails that need the calcium in harder water. The small common pond snails are helpful too, and they will usually manage if the water is not too soft. On that, any idea what your GH and KH is, out of the tap? You can ascertain this from the water supply folks, they may have a website.

As for an algae eating fish, there are some for a 20g, but first consider that this is a small space and every fish is adding to the bioload. Otocinclus would be fine in soft water and the tank size, but they need a group of at least 3. I would suggest that you get some plants, and if there is an algae issue after the tank is more matured (usually 2-3 months or so after plants) you can consider otos (or something else) then. As something more interesting that is excellent for common green algae (which is all the otos will touch too) have a look at Farlowella vitatta. One on its own is fine. It attains 6 inches but this fish is so thin that this is not an issue. Another oddity is the Whiptail Catfish, again singly is fine. All these three will eat diatoms too, but as we said previously, that is a temporary issue and will be gone.

To your question on plants in the previous post, I have not bought online but some other members have and I'm sure they will suggest reliable suppliers. Also, depending where you live it may be possible for other members to sell or give you some plants. If you were close to me in Vancouver, Canada, you could plant your tank twice over with plants I would gladly give you. I won't mail out of Canada though, the delays at the border have been discouraging with dead plants resulting.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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