A friend of mine has two of them, she got them about the same size as that fella which was in June of last year, they are now about 4 1/2 inches long from snout to tip of the tail. They currently are in separate 10 gallons with other fish as well as with a good filter. Frequent, regular water changes are given and they are fed algae wafers as well as some (microwaved in water) cucumbers and squash (to make them soft).
They are healthy and happy and can stay in a 5 gallon or 10 gallon by themselves for a while. People usually flip out when this is said since this really isn't a permanent tank.. Some pet stores (like our local one) will take in Pleco's who have outgrown their home and will trade you for a smaller one.
They do get very large like this photo below:
Typically when they reach such a large size they will start eating smaller fish in the tank, which is always a risk, but that usually doesn't happen until they are quite large.
I'm telling you, the OP, this because I want you to know that for right now, you taking this fish and placing it in a 5 or 10 gallon with a good filter (hood too cause they do like to jump sometimes) and a nice diet of algae wafers and blanched cucumbers and squash and even some romane lettuce will be fine for atleast a year until you can either find him/her a better home, a petstore who will take him/her or even grabbing yourself a larger tank and keeping him/her for yourself. ANYTHING is better then that tiny little bowl.