I had a big problem with my main canister filter this past week- most of it is detailed on the forum where I asked for some help. Long story short the canister body cracked near base where I screwed input fitting too tight. Saved from a flood by the fact that I had it sitting in a tupperware bin to catch such an incident, and the leak was slow. I shuffled filters- put the HOB biowheel from the swordtails' 20g tank on the main, went out and bought a new internal filter for the 20g (because I couldn't find a sponge filter at store, and my spare was running on the shrimp container), and put what media from the canister wouldn't fit in those filters, into buckets with airstones running, to try and keep most of the bacteria colony alive while I wait for replacement parts.
I learned a few things from this. Overflow bin a very good idea! Hand-tight doesn't mean what I thought it did. I'm pretty good now at managing emergency setups in a pinch: have been testing the waters daily and none of my tanks show any ammonia or nitrites even though their filters got changed out and the temporary replacements have less capacity. Tested the little shrimp bin too- they were fine as well. While all this is going on, I am still treating those two tanks for parasites with API General Cure.
Also learned: having extra equipment around is a very good thing, even though I get irritated at clutter and try to sell/give away things I don't use anymore. I find after a few days I actually like this internal filter on the 20g better than the HOB so I'm thinking of putting the biowheel back in a box and just keeping it for a backup to use on the main in case of emergency again.
Also learned: I am definitely at my max number of tanks. Having five things running in my living room (plus the betta tank upstairs) felt like too much for me. My main tank, the 20g with swordtails, the temporary bin for shrimps, and two buckets of filter media with airlines to house the bacteria while I resolve filter issue. It was enough to handle already having the shrimp bin running- because it is a constant thing on my mind, checking on them several times per day, testing the water to make sure no cycle happening, siphoning out a bit of waste and replacing with some new water, monitoring the food to make sure I'm not putting too much that's not eaten (the shrimps are not very active due to the cooler temp) etc. With the two buckets that's another thing- I glance in there every time I walk by to make sure the airlines haven't clogged, and the hum of two air pumps running in this room is aggravating, and I can't imagine how people do it, keeping multiple multiple tanks. It is too much for me to think about and care for. Definitely three is my max. Throw in a hospital or QT tank running for some reason and I'm at the limit.