[Sk8r]

1. antibiotic. [greek: against-life]-- a medicine that kills bacteria. If your newly bought sponge and rubber gloves say they have antibiotic or bacteria-killing properties, don't use them in your tank.
2. gram negative and gram positive bacteria: this relates to a bit of lab science, how these bacteria sop up dye when on a slide...This wouldn't matter, except it relates to how they sop up other things, like antibiotics. Some antibiotics work only on gram negative bacteria; some on gram positives; and then there are 'broad-spectrum' antibiotics---that work on both, or either. The sand and rock bacteria in your tank, those good guys you cycled to let breed---are gram-negative. The way in which anti-red-slime treatments work is that they are a gram positive antibiotic, which kills off any gram positive bacteria and leaves the gram negatives alone... BUT... my own experience says they also do a number on the biodiversity of the tank at a microscopic level: after using it, I suffered a copepod die-off and had serious problems keeping my mandarin alive, so be advised. Copepods feed on algae, among other things, and you want them.
---And: postscript: not every antibiotic, works well on every disease: that's why your human doc bothers to diagnose your illness before giving you a very specific antibiotic. He knows whether your disease is gram-negative or positive, and also whether, say, tetracycline is going to make a dent in that particular bacteria---or not, even if it's the 'right' type. So do a little reading over in the disease forum before treating: ask what's actually CURED the disease---and for the love of your tank---do NOT dump any antibiotic into your display tank!

Do you get that you can save yourself a world of hurt (and give your fish a safer, nicer start) if you quarantine and never end up with a bad bacteria (or crawly parasite) loose in your display tank? Note I say 'quarantine.' Don't treat well fish. Just observe: sickness tends to pop up a few days after the excitement of being bagged and transported and put in new water---the same way you know that once finals week is over and the adrenaline sinks, you're going to catch whatever's going around and be sick for your vacation. If your fish is in a nice separate tank, you can deal with it; if he's 'sneezed' into your tank---your display tank now has some bad bacteria (or a hitchhiker) that you don't want, and it's impossible to ask the newcomers for a proof of residency, eh?

3. kalk---a cheap source of calcium/buffer for your tank, if you have stony corals, and if they are starting to need more dosing than you can sanely provide. Kalk drip is usually enough for tanks up to 100 gallons. Above that a calcium reactor is the choice.

4. GFO, or granulated ferrous oxide (a granular iron/oxygen) binds up phosphate. In a GFO reactor, it will suck all the phosphate out of your tank and make it SO green-free it may starve your algae-eating blennies, so don't go that far if you have blennies. You may need to just scrape a bit. But it is a cure for hair algae problems, or any sort of green algae.