i see where this is going, hardy fish, cleaning fish, your wanting to take the easy way out and do minimal water changes right?
Truth is there is no way out of having to change out the water and do alittle gravel vaccumming. A tank is a closed in area so nitrates are bound to build up regardless of fish selection. 10% tank volume weekly or 20% tank volume bi-weekly is a good number to follow to change. Plecos will graze algae but will not "clean" the tank, they like to nibble on driftwood and munch on occasional veggies. Good ol fashion maintnance is your best bet. If you do go the pleco route def. avoid the Common Pleco
which grows to be about a foot and a half if not larger. A Bristlenose Pleco
will grow to about 5-7 inches and prob. be a better choice. I would avoid ottocinclus atleast until your tank is stable and established with some algae to graze as these are sensitive. Corys always make a nice addition. They are shy and timid unless in a school of atleast 6.
BEFORE ADDING FISH, learn about cycling your fish tank. Google.com and type in "fishless cycle" to learn how the water chemistry works. To quickly sum it up, ammonia converts to nitrites which converts to nitrates which get removed by water changes. If you have trouble with the cycle please feel free to ask questions and im sure someone wont mind assisting.
After cycling a tank good starter fish would be, but certainly not limited to or all at once:
-A school of neon tetras
-Guppies, Mollies, or Swordtails
-A school of tiger barbs
I recommend picking up a liquid test kit. API makes a decent one call the "master test kit" that sells for $25-35 in stores but about $20 online. Regardless of brand you want atleast an ammonia, nitrite, nitrate, pH and thermometer to keep close eye on your water conditions.