I've kept fish tanks for years and I'm finally ready to do it right. For my first question... what causes the white, scaly buildup at the top of my tank? It gets all over the top of the tank and glass cover. I'm guessing it's calcium or lime? My water source is city water (not a well) and I treat it for chlorine and chloramine. I'm starting up a new tank and need to know if there's anything I can do to prevent this buildup.
How hard is your water? What temperature do you keep your tanks at? Excessive build-up is probably due to a combination of very hard water and/or high evaporation. Any thing you can do to reduce evaporation will help, although I can't think of any easy way except lowering your tank temp - the room temp and humidity also affect it.
Filling the tank right to the top will reduce build-up on the sides. You can try various things to try and reduce build-up on the glass cover - what comes to mind are removing the cover alltogether , removing part of it so more evaporation can escape, tilting it so some condensation flows back down into the tank... It's not a big deal, but if you're growing live plants, it is important to keep the glass cover pretty clean, both from limescale and just plain water condensation.
Perhaps I should explain further - I want to create a river tank with pools and a waterfall. I'm concerned that I'm going to get this buildup inside the tank on the waterfall and tank sides - making it much harder to clean. I've got a couple of decorative fountains in the house and this buildup is all over them too.
You can also put some vinegar on a cloth. The vinegar will help dissolve it better, then use another cloth with some water to wipe away the vinegar. A little vinegar in the water won't hurt the fish, but it's still worth getting off as much as you can.