Green Algae and unchanging freshwater tests

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adpearce

Aquarium Advice Newbie
Joined
Mar 8, 2022
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Help! I've posted before, but I have sudden green algae on my substrate and decor. The water has a greenish tinge too. I've tried turning off the light for a couple days, but it's still there, and my cory cat isn't doing much in clearing it. I have 2 mystery snails, 6 platys (3 are about 2 months old) and my cory cat. I also cannot get my nitrates or nitrites above 0 with my api test. Ph is 8.2 (a bit high) and Ammonia is 0 or very close to it. I need suggestions on the green algae, as well as the water parameters! Everyone seems happy and healthy, so I can't figure out the cause! I have a little duckweed I got from my lfs, and some plants propagating, would that add to it? 10 gallon tank.
 

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How long are your lights typically on for? Does the tank get any direct sunlight?

Likely cause is too much light. Lights should only be on for 6 to 8 hours per day and the tank shouldn't get direct sunlight.

Turning off the lights for a couple of days wont change anything. You either need to reduce the lighting period over a much longer period of time or, assuming you dont have live plants, a complete blackout of the tank for a week or so. If you go the blackout route no light whatsoever, cover with a dark blanket, lift the blanket in the dark to feed.

If your tests are all zero, there is possibly something wrong with your tests or you are testing after near 100% water changes. If you are cycled you should see nitrate, if you arent cycled you should see ammonia and/ or nitrite depending on how far really along your cycle has progressed. Make sure you are doing the tests properly, as per previous thread really give bottle #2 of the nitrate test a good shake, bang it on a counter top. If that still doesnt show anything get a 2nd opinion.

It could be the duckweed is consuming all the nitrate however, so if testing really shows everything is zero i wouldnt worry too much. I would however get an all in one liquid fertiliser that has a good amount of nitrogen as the plants wont be getting enough of this essential nutrients from the water. Something like NA Thrive if its available in your country of origin.

Your platys will eat a little algae if they are hungry. Mystery snails arent as good algae eaters as nerite snails, and a cory will have a go at it if they are starving. You dont really have any known algae clean up in the tank. And nothing will eat the algae causing the green water.
 
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A handy thing to remove green algae is a piece of new kitchen sponge. Cut a small piece maybe 1" wide and wipe along decor, substrate, and glass to pull it out - rinse sponge - repeat. I've wiped plants this way too.
 
It will take a few rounds of wiping it off, but if you follow Aiken's advice, especially about light, eventually you'll beat it or at least reduce it severely. Just keep watching for it and remember the glass sides and plants to wipe off. I have nerites and mysteries but no one touches that green algae. I did the other things he suggests but it wasn't until I limited lighting to 6 hrs/day that I began to have less and less, pretty much to nil, of algae. Too bad, I love seeing everything like up like a nuclear christmas, but that's how it is.
 
Buy the cheapest filter with a UV bulb and it will be gone within a few days. Leave it in until the tank stabilises job done.
 
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