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so im going to my lfs soon and i need to see a pic of a normal pleco belly and one with a sunken belly so i can know which ones are healthy there

Hi,

a normal belly:
Ancistrus sp. "L 107"


a sunken belly:
Acanthicus adonis

Just avoid any with sunken bellies. Flat bellies are OK.
Plecos in a fish shop will often not have fat bellies because they may have gone several weeks with light feeding.
Major exporters, importer and wholesalers do not like to ship fish which have full digestive tracts because to do so can cause the shipping water to become fouled and depleted of dissolved oxygen. Fish shops rarely take the time and trouble to fatten up their fish since they too are just passing through. You will get very healthy fish from hobbyist breeders. For example, I always withhold feeding my plecos for a minimum of 48 hours prior to when I intend to bag them for shipment to allow them to empty their digestive systems to avoid fouling their shipping bag water.
Major shippers feed their fish as little as possible because they have a quick turn over of their inventories. They can't afford to not have their fish ready to ship out on any given day.
Daniel's photos are very good examples of what to look for and what to avoid.

Mmm if you can find a breeder or aquarist that has what you looking for go for that as he will generally have looked after them better. Sunken belly is quite easy to see though and you should avoid buying these and point it out the seller so he can take care of it.