Curious to find out if an oscar has lived in a pet shop all its life in a small tank and/or poor water qualities can it impact on the fish when they are older, will they grow slower and smaller

Harmful conditions can have long term health effects on a fish if they are kept in the poor conditions for too long. The fish can suffer long term liver and other organ damage leading to a short life span. Poor water conditions can wreak havoc on most organs in a fishes body.

If you keep an oscar in too small a tank then you will get health problems from poor water conditions. If you managed to keep the water ok the fish can still end up stunted (they dont grow to full size). In Oscars they look odd shaped and deformed. Also in stunted oscars the internal organs still grow and get too big for the fish so they get problems from that and live a shortened life

good advice all around

albinotiger wrote:

but most fishes in the lfs stays there only for a while.... in most cases, 3 weeks
the most, otherwise, they all die.....(that is here in my place since most lfs
operates in a concessionaire arrangement). in that period, whatever environment the
fishes had, that is the damage they could get....a newly delivered merchandised
has a high chance of good health, the longer they stays in the lfs, the more damage
they got....