Find someone responsible you know, and PAY THEM. Don't bank on them saying they'll do it out of their generosity, because people get lazy, and their first thought will be "he's not even giving me anything, so what if I miss a day or two". Pay half up front, and half when you get back, so you can make sure everything is alive and well before you hand over the rest of the money. People are more likely to put a little care into something they're being paid to do, vs. doing for free.
Train him, write down directions/steps, etc. As easy as it may seem to you or me, it might be rocket science to someone else and the less they have to think about, the better. How much is your top off every day? Maybe get 5 empty water bottles and label them M-F or whenever you're leaving so all he/she has to do is pour in a bottle a day. Also, if you use flakes, get a pill box from Walmart or Target and put the correct amount of food in the box so all he/she has to do is open that day's box and dump it in.
