My plecs make a bit of a mess every now and again but they're nice to look at. Unfortunately, a lot of species need more room than 90l as they tend to grow big. If you're looking for an algae eater then your ancistrus (bristlenoses) are the best kind. There are many colour morphs of the common bristlenose, and many other ancistrus types such as the l183, l144 etc. These also will not outgrow your tank.
If it is just a plec for viewing that you would like, I personally like the l333, l129, l201, l340 and l387 for a start, none of which will grow over 6 inches.
Just be warned that any pleco species will likely wreck echinodorus leaves and occasionally dig stuff up. If it's just a cleaner upper you're looking for, then ottos are far better suited.
