I have designated 40ltr buckets for each tank, blue for one, black for another, green for another. Purple for QT/hospital. The buckets work a double job as equipment holders but also used for cleaning filters.
In each bucket is an attachment for the draining hose (specified to the substrate in the corresponding tank), a short hose for filling the bucket, nets ranging in size suitable for the fish in the tank and a snaplock bag with a note book (same colour as the buckets) for logging test results in.
This means that my nets and draining hoses don't move from one tank to another lowering the chances of contamination between tanks. It also means everything is in one spot so if something goes wrong, its all there.
Next time I'm at my ex's I'll take a pic of one of the buckets to share - if I remember, I have a mind like a colander..
I also have a large container with random PVC pipe and filter nick nacks in it, spare heaters, air pumps, bio media, etc. Handy to have lying around.