as said already .5 ammonia is your problem. Do the water change, and monitor ammonia especially over the next couple of days.
Try and work out why the ammonia went up.
A common pleco would get far too large in due course for a 30 gallon in any event and is a messy fish - what size is he now and do you have adequate filtration.
Try and work out why the ammonia went up.
A common pleco would get far too large in due course for a 30 gallon in any event and is a messy fish - what size is he now and do you have adequate filtration.