what are thse marks?

[Sophienlee2308]

Hi all,
just noticed that my golden nugget pleco has several white marks on him that looks like some scales have lost their colour. noticed it whilst feeding him, he has a large patch by his tail and a few around his eyes. ive attached pictures below.

we did try to look it up but there were several answers (fighting, heater burn) although it couldn't be the heater as he is in a juwel tank in which the heaters are in the filter. some other people said that they can change colour depending on their moods but wasn't sure if it was all over their bodies or in patches like he is.

can anyone tell me what these marks are actually from?

are we feeding him the wrong things(he has cucumber, pellets, algae wafers, garlic tablets)?
is he fighting?
could it be ammonia burning him (ours hovers around 0-0.25ppm but mainly 0)


thanks

sophie and lee

[TropicalFishForums]

[Sophienlee2308]

also just noticed that the marks are now not so white and the on his tail is a lot smaller than it is in the pictures. the mark on his tail got smaller after he had eaten from an algae wafer. and we done a test on the tank and ammonia was at 0.50ppm with API freshwater master kit so we are doing a water change. not sure if the ammonia is there for an unknown reason or whether it is higher due to feeding them less than an hour ago?

but doing a water change to be on the safe side.

[plankton]

Feed him some protein, they aren't veggies. I think that may help, as it looks like there's something missing from his diet.
Try to keep the parameters (especially ph and hardness) as stable as possible, they are very fussy about the water.