Is this pale coloration normal for plecos?

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Apr 2, 2002
New York
Just a quick Q. Do you have a cave for this fish and if so, how big is it? If not a cave does it have another form of hiding place similar to a cave? Spkotching in pleos is not uncommon. Stress and fighting are two frequent causes.

One quick observation re .25 ppm of ammonia. Sometimes this is a false reading. If it is peristent at that level, then it is likely a false reading. One way to know if a constant .25 ppm ammonia reading is real or not is if there is any nitrite present. The bacteria multiply as the result of there being more ammonia than they can consume. So, in a tank where there is more than they can consume, they multipy and they make more nitrite. Because the nitrite bacteria reproduce more slowly than the ammonia ones, excess ammonia being processed should normally result in excess nitrite that cannot be handled quite yet. Another clue to this sort of situation us that there is nitrate being produced and you can measure that and see the level rising from testing.

Here is another way to try to understand a constant .25 ppm of ammonia reading. Set up a new tank. Plant or don't plant as you choose. Now here is what I want you to do. I am going to show up an random times and days to test the ammonia in that tank. Your job is to make sure that no matter when I come to test, the result will always be .25 ppm of ammonia. I have left out fish to keep the challenge easier, but you can add them if you think it would matter. Tell me exactly how you are going to create a tank which always reads .25 ppm of ammonia no matter when it is tested. One last consideration, your answer cannot involve the use of sophisticated technical equipment the average fish keeper will never have. This challenge will help one to understand why a constant .25 ppm reading is almost impossible to be accurate.
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AC Members
Mar 21, 2020
Imo, he just looks stressed out because he doesn't have a cave. Give him something (anything aquarium safe to hide under) and some fake plant for 'brush' to disguise in and see if his lighter areas become more uniform.

My BN plecos change color (splotchy) often when they confront eachother, when they are calm they are very dark. But if they are stressed they will have lighter shades mixed in.

Have you tested your tap water for ammonia and nitrate?

0.25ppm ammonia could be a blip in the API test. Does it ever register higher? What does bottled water test at for ammonia with your test?
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