Here's something I snagged from a post a while back. Some are better than others.
Pipe Cleaners - nope not Liquid Plumber or Clog Blaster - these really were designed to clean out tobacco pipe stems so are like nano-bottle brushes - just the right size to clean out the usual size of air hoses we see in the hobby:CPR backpak hoses/other skimmer hoses. You can get these at Michaels or other home craft houses very inexpensively.
Old toothbrushes - great for cleaning powerheads and whatever else. Even better for larger areas are denture brushes or small vegetable brushes...
Wet/Dry Vacs of any size.
Bridal Veil fabric - comes in two sizes of mesh - usually see this as the stuff that holds the rice or bird seed to chunk at the bride and groom as they leave the ceremony. Usually used to wrap and hold zoos, palys, xenias and other soft corals to rocks we hope that they will put down roots on. I've used it for many things - repair nets, hold carbon and other filtration media, even cradle monti frags along the sides of the tank as a space saver - the montis didn't care and continued to grow.
Synthetic pillow stuffing - Hancock Fabric - used to use this as HOB filter material as it is inert and the same stuff you see in the nicer packaging at the LFS for far more - you can get a bed pillow-sized bag of the stuff for around $2.00 and just tear off what you need for your filter - cheap enough that you can change it out a lot more frequently as well.
Carbon granules - Home Depot/Lowe's - garden dept. They sell it for use in outdoor ponds. Far cheaper there than the LFS. Activated carbon is activated carbon is activated carbon.
White vinegar - the cleaning agent of choice for so many things salt water. Albertson's or any store brand - the cheaper the better as it's the same chemical and usually the same strength regardless of price and label. I use it straight for most of my cleaning as I'm not as patient as Marc..
Clips - yep, Dilbert was right - 'Better Living Through Office Supplies': those big clips work well to clip plastic bags to the side of the tank while acclimating or to hold air lines/water lines/power lines where you want them...they tend to rust up after a while but the iron seems to be good for the tank (hey, it's a Miracle Mud Ingredient!)
Mini-food processor to grind up frozen krill, fresh shrimp, etc. - Walmart - around $15 or so - they look like a mini-Cuisinart but are far easier to store and clean...so you can make smaller lots more often...
those big, heavy-duty plastic bags saved from your last LFS coral/fish buy - save them for when you need a quick isolation tank or want to move live stuff from one tank to another and need to float stuff for a while...
I'd also add:
A turkey baster or sea squirt. They are very handy for all sorts of stuff like blowing off stuff and getting a little tank water to add to frozen foods.
Another thing I've found a use for is one of those long plastic shoe horns with the back scratcher (a little hand) on end opposite the shoe horn. You can use the hand to scoop out small stuff easily. The shoe horn part can poke or pry in the tank and also depending on how you move it, can create small currents to "blow" the sand off the live rocks. I find myself using this device quite a lot.
Auto top off. This saves plenty of work and trips to the RO/DI area.
This might not be as cosmic as your dialysis machine, but they make life a little easier.
