Pictures of the fish when its white and when it's brown?
Picture showing the entire tank with the tank light on?
What other fishes are in the tank?
Have you added anything to the tank in the 2 weeks before this started?
How long has this problem been going on for?
What is the ammonia, nitrite, nitrate and pH of the water?
What sort of filter is on the tank?
How often and how do you clean the filter?
How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the aquarium?
What else do you feed it besides pleco pellets and what brand is the pleco pellet food?
I haven't added anything to the tank in years. Undergravel filtration with a supplemental sponge filter for polishing, it's due for a water change, but that doesn't seem to be it, will see if I can find you some pictures. Of course I use chlorine remover. He mainly cleans the leaves and the tank and flake food. I've found too many pleco pellets grow a lot of red brush. I feed Hikari. I clean half of the gravel when I clean the tank. He's been changing color intermittently for the last 6 months. I suspect old age. I do 50% water changes monthly. much nitrate removal is probably handled by giant anubias nana in the tank
I have not been feeding pellets often enough and he latched onto that one when I dropped it. maybe he changes color when hungry, he is his normal pale pink self again this morning.
The fish looks fine and could be changing colour when excited or stressed (possibly excited at feeding time?). Is the fish a male or short bristled female?
Are there any other bristlenose in the tank it can breed with or has it been alone all this time?
About the only thing I would do regarding maintenance is water changes more often, maybe every 2 weeks instead of once a month. Apart from that everything seems fine.
He is all boy. His female died after I put the cave in I think. I have not been able to find a body, the guppies may have cleaned her up. That would be about October. The only females I have here are his daughters and they are a bit small for breeding, about 3 inches long. Lost my other adult female to red cyanobacteria in the 55. They were both about his age. during spring I do well to manage monthly water changes, i just try to get them caught up in winter and again in summer
Bristlenose normally leave a skeleton behind if the other fish eat their body. They have a pretty solid skull that only has a think layer of skin over it so even if the body gets eaten, you usually find the head.
What time of day do you see the colour changes?
If it's first thing in the morning when the lights have just come on, it could be nocturnal colouration.
I wouldn't worry too much. There are no fish diseases that cause fish to go brown and then back to their normal colouration so it's most likely natural colour changes caused by the fish in response to something.
his daughters are about 2 inches right now, he's a good solid 5 I think. I got a brownish pic a couple of days ago, but after pellets 2 days in a row I wasn't buying the starving fish act, maybe he gets tired, typically it's 9 or 10 pm when I see him brown
Alice B, you are definitely doing something right if the fish is 12 years old! Personally, I wouldn't change a thing. I too have fish that are very old and can say for certain they don't live long lives without exceptional care. Continue your excellent care and let the fellow live out his senior years in comfort.