I love the KISS theory and Occam's razor.
I never unplug my heaters or my 18 AquaClears when cleaning tanks and filters.
All heaters are placed horizontally on the back glass as close to the bottom as I can get them (within reason). This is always a few inches lower than where normal water changes drops the water level, Plus placing them that way gives me the maximum benefit possible from a heater.
All of my AC filter intakes have prefiler sponges. If nothing else, I always remove the intake assembly to get the prefilter sponge off. But, That prefilter should hold a bunch of gunk I prefer not to release back into the tank when I go after the sponge. So I use a brine shrimp net which goes over the intake sponge and then I lift the entire assemply out of the filter body. I rinse the sponge, put it back on the intake and re-attach the intake to the filter.
I Ddo this in a way that it will not intake water. I do not put ot all the way down in the filter so it doesn't sit atop the impeller. I rotate it clowise toward the basket and it catches on something so it won't lower. But before I do this I pulle the basket and rinse the foams in it and I replace the floss that goes between them unless it is not badly clogged with gunk.
When I am done doing tank work and am refilling the tank, somewhere during that process, I rotate the intake back into position over the impeller and lower back in place. Of course the end of the intake has to be submerged some to work.
My problem is not every piece of equipment lends itself to a solution and therefore, must be unplugged. Canisters are an example as are sponged powerheads. I rarely fail to plug a canister back in but those powerheads and some air powered things where they are turned off and on with a valve on a manifold I sure can forget tore-open when maint. is done. This is one reason why I normally have multiple filters on most tanks.
