honestly back in romania (1990's), i had a home made air pump, and a home made heater
with the air pump i created a water column that was filtering enough good my tank and that was doing both surface agitation and currents in the water (so you make sure your water has same parameters all over)
once the electricity went off, and i was away for 2 weeks, none the thermostat and the air pump worked for about 10 days and my fish were just about fine.
truth is that my plants were reduced to almost nothing ... but still ... they grew back up
SO as long as they have something to eat, and to breathe ... your fish will be fine.
and of course you have to make sure you are disease free in your tank.
do not need to be scared, keeping fish is not that HARD of a work.
BUT, with nowadays technology, you can make your fish live longer, happier and healthier ... so why not ?