I once had a dream where my three different tanks (at the time, FW SW and goldfish) had all had a bunch of fish added, but the fish were in the wrong tanks- goldfish in SW, SW in FW, etc. I spent awhile capturing everything and just putting all the new fish in cups of the right water. That was kind of weird.
Also had a dream where I somehow had two cleaner shrimp, they bred like rabbits, and then they all mutated into flying cleaner shrimp and just flew around swarming people and cleaning them. Spent some time chasing cleaner shrimp with butterfly nets.
Also, I once got up in the middle of the night, half-asleep, because there was a weird noise- and I stepped in a puddle. The tank causing the puddle was 6 feet away. Something went very wrong with the HOB filter on my 65g, and it kept pumping while pouring water out the back, so I ended up with about 7 gallons of water all over our 100+ year old wood floors. Also under my bed, under the stand, under another stand, and all over the place. I was half-asleep the entire time and kept thinking "I'm probably dreaming, but I should keep cleaning this up anyway."
Turns out I wasn't dreaming. Yaaay.