should have paid more attention... you asked several questions... sorry.
i have had them a little over a year. they are easy to care for and need no supplemental food if not overstocked and residing in a community tank. they will also wrestle anything about their own size for food until they learn there lesson. shrimp are great for algae control and cleaning up extra tid bits of food. amanos are among the top rated for algae control.
i'd say if you want to add inverts to your tank you should start feeding an extra pinch for about 2-6 weeks prior and test ammonia, nitrite and nitrate until your levels are real low. if your you've had your tank up for a while you could just add the pinch for 2-3 weeks and skip testing to make it easier.
for shrimp hiding places are crucial, alot of them need to be able to climb just like reptiles, hence the lava rock and hollowed log in the front of my tank. i think your tank will liven up nice with a real odd pleco a (bristle nose will contrast nicely) and some really colorful snails.
check out the classifieds at aquariacentral.com (these guys are usually happy to answer compatibility and requirement questions). they also have special threads dedicated to giving away unwanted/unneeded items from fish to plants to decor and equipment/supplies. you can google RAOK (random acts of kindness [pay it forward]). it works like this: one person posts a list of things they would like to get rid of... the next person claims it, pays only shipping and posts a list/pics of things they'd like to donate to the next person. it helps everyone... we get to get rid of our junk without funding another shady pet store in the process and we get amazing prices on things that otherwise would be thrown out or eventually killed.
right now there are a couple people with great, longstanding selling records getting rid of some beautiful shrimp and snails for real cheap. one of their moderators also likes to do bulk purchases of rare items and pass the savings on to the other members... he also quarantines and fattens them up before offering. these guys (the better sellers) are real big on including at least 1 freebie also