This is really where the fun begins. I put a large pot with half of the amount of water 
for your gelatin on a lab hot plate. Let that water get really hot, although I don't think 
that it has to boil. Add the gelatin powder and throw in the stirring rod that should 
come with the hot plate or just stir it for a while yourself. After the particle look 
disolved, turn off the heat. Then you can throw in the remaining half of the water. 
Make that water cold to help cool down the mixture (adding scalding water to the 
tanks is what cracked some of them). Stir a little bit, then fill the tank. We filled the 
tanks by siphoning the mixture. This may also help prevent cracking due to heat. 
The gelatin mixture we used was 1.5 wgt.% powder. This means that for one tank 
the mix is 6 liters of water and 90 grams of powder.

Good luck!

Jordan

[90 grams of powder = ~145 ml of powder.]