Join Date: Apr 2014
Location: Philadelphia, PA
So lately, I have been looking into making at least a tank (and then a whole fishroom) completely automatic. Feeding would all be automatic. Automatic water top-offs. Automatic lights (and you could automate the CO2, as well but I don't use CO2). It *can* be done. And beyond that, you can get away without water changes for two months (you learn a lot about tank sustainability when you go to boarding school).
As for top-offs, there are automatic top-off systems out there. Don't go for the float valves but instead the electrode sensors. Those will run between $80 and a few hundred (but there are good options around $100 if you look). Set up a pump in a close tub and you're good to go.
For lights and CO2, basic outlet timers work.
For feeding, Eheim makes a nice feeder that feeds my turtles and tilapia. I find they go about a month before needing a refill (so you would need a friend to stop in maybe 3 weeks in, and then 6 weeks in to fill up).
As far as the fertilizers go, if they are in liquid form I'm not sure what you can do. However, if they are in a powder form it may be possible to bind the powder with something (like they do fishfood) to make pellets which could then be dispensed in an automatic feeder.
I have invested a lot of time into figuring out how to set up self-sustaining tanks that can run for at least a month without maintenance. Other than fertilizers, everything else above should work and help your situation.