gold nugget Pleco turning pale

Hello

i brought a gold nugget pleco about a month ago 3 inches long, i have been keeping fish for 8 years now but this is my first pleco, i noticed 3 days ago that he was turning pale on his body and it has slowly spread over his back. other than that though he is still very active and eating well, i am feeding him mostly on courgette and he probably finds some bloodworms the other fish missed here and there. the tank is not brightly lit, it is a planted tank with plenty of rock caves he hides in and with large amounts of driftwood, non of the other fish are exhibiting any symptoms
-its a 450L aquairum
-nitrites and ammonia are 0
-PH is 6.5
-Temp is 26 degrees C
Stocking:
8 juvenile platinum angels (largest is about 3 inches tall)
the pleco (more fish on the way)
the tank is also quite heavily planted if that makes a difference

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Kind regards Jack

im reading about sunken bellies i have no idea how to tell a sunken belly from a plump one on him so heres a pic

Hi and welcome to the forum

It could be a bacterial infection, however there is no red around the edge of the pale area so unlikely.

The fish could be showing stress colour but if it came on suddenly (it's been going for 3 days) then that is unlikely because you would have noticed it before now and it would usually happen in the morning when the lights first come on. Then a few hours later the patch would go back to normal colour.

It could be a Microsporidian infection, which causes the muscle tissue to turn white but it's a bit hard to tell on dark fish and catfish are not renown for getting this. The only cure I have found for Microsporidian infections involves getting the water to half strength seawater and keeping it there for a month. Unfortunately this will probably kill the catfish and all the plants.

The most likely cause is a protozoan infection. The safest way to treat protozoan infections is to raise the water temperature to 30C and keep it there for 2 weeks. If there is no improvement after a 4-5 days then it could be something else or might need a broad spectrum medication to treat it. Unfortunately with catfish you have to be careful about what medications you use because catfish are scaleless fishes and don't tolerate chemicals that well.

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I would try raising the temperature to 30C and keep it there for a couple of weeks and see how the fish goes. When you raise the temperature, increase it 2 degrees today and then 2 degrees tomorrow so the temperature goes up over a couple of days.

Before you raise the temperature, wipe the inside of the glass down, do a 75% water change and gravel clean the substrate, and clean the filter. Then increase aeration/ surface turbulence. The warm water reduces oxygen levels and you need to increase aeration/ surface turbulence to try and maximise the oxygen levels in the water.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

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If there is no improvement after 4-5 days at 30C then look for a broad spectrum fish medication that treats bacteria, fungus & protozoan infections. Check the directions for use with scaleless fish. If there are no instruction for using the medication on scaleless fish then only use it at half strength.

To work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.

When you measure the height, measure from the top of the substrate to the top of the water level.

If there is no improvement and you do decide to use a chemical medication, reduce the temperature back to 26C before you start treating. Keep the aeration and surface turbulence going during treatment because medications also reduce the oxygen in the water.

Remove carbon from the filter before treating or it will absorb the medication and stop it working.

Wipe the inside of the glass down, do a 75% water change and complete gravel clean. And clean the filter before treating.

thanks for the info! already ordered a temporary tank to treat him in dont really like the idea of keeping the other fish at that high of a temp, in the mean time ill treat the tank with anti white spot treatment as that is also a protozoan should have a treatment tank up within a couple of days