Melody
Dec 3rd 2006, 02:23 PM
The Tetra (http://www.tetra-fish.co.uk/tetratropical/calculators/index.asp) site has a fantastic collection of useful calculators for the hobbyist, including treatment calculators for their products, as well as calculators for stocking levels and volume. There are two water change calculators, one of which covers collecting rainwater to soften your water.