1) In order to “quarentine” a fish or plant (plants, gravel, fish, everything *can* harbor ich), it’s typically a good idea to get a small tank (5-10gallon) and set it up for a period of time and watch the fish/plant/etc. to make sure that there’s nothing weird going on. This will help if, for example, you put in a feeder fish ($.05) with your discus ($50+), and don’t want to risk your expensive fish. Or if you just want to keep a solid tank up and running disease-free. Now, you “ought” to do this for around 2 weeks (depending), and this will eliminate the chance of you bringing in any diseases or bacteria, fungus, etc. to your tank. However, I personally take the time to do a really thorough scoping out of a store before I buy, get their ship dates down, and look at an entire tank for a few days before I buy. I’m a bad, bad person for not putting my fish and plants in quarentine, and I know it’ll bite me in the butt at some stage, but right now I simply don’t have another heater for it – lame, I know, but my main tank has a pH difference from everything else of -1.0, which is pretty significant. Anyway – you “should” and “ought to” quarentine before tossing fish/plants into your tank … but I know of quite a few people who do not, and if you’re buying from an LFS, you can do a lot of legwork on the front end and save yourself some trouble on the back end. This is in my experience – someone else will come on here and repeat that, yes, I’m a bad, bad fishkeeper for not keeping a quarantine tank at all times. Just another point – I would really recommend getting a HOSPITAL tank – just like a quarantine tank, except this functions AFTER the fish/plant is diseased, and keeps your medication focused on the afflicted, rather than going all over a healthy tank and adding potential problems. Okay …
2) Bleeding gills are typically a bad sign. Now, gills are supposed to be bright red, as this is where all the oxygen is being exchanged, but if they are actually bleeding, then they’re likely either burned (check your Chlorine and Chloramine!!!), it’s a pH shock (too acidic) … um … gill flukes if you have goldfish … and that’s the extent of my knowledge on bleeding gills.
3) Ich CAN and WILL open the door for secondary fungal or bacterial infection – it’s a parasite that drills holes in your fish and swims around just under their skin … not a good thing. With stuff like Rid-Ich, remember to ALWAYS treat for at least a day after the cysts drop off the fish – follow the instructions on the bottle to the letter. Also, on tropical fish, it’s typically a good idea to give them salt baths in the early stages (too late, and they’ll have physical holes drilled into the fish, and it gets hard for them to retain fluids then), turn up the temperature (80F is adaquate – more is NOT better, though!), and remove any carbon that you have in your hospital tank’s filter. ‘Course, if you notice ich in your main tank, treat there … unless you have clown loaches, then you’ll want to move those (and other “medication sensative” fish) to the hospital tank and observe them, and treat the whole tank … Carbon will eat up medications and your money at that point.
So – what can you do to stop ich?
Identify early; do your work in looking the fish over, and asking about tank disease history at the LFS [cheap, easy].
Set up a quarantine tank for fish to spend a week or so in BEFORE going into your main tank [somewhat cheap, depending, and somewhat easy, depending].
Get a hospital tank set aside for your fish when they do get sick [somewhat cheap, really easy].
Get your meds for fungus, bacteria, and ich NOW, before you have problems … ich and other nasties typically crop up on the Thursday night before a 3-day weekend [you’re gonna buy them anyway, simple].
Spend some time every day looking over your fish and learning their behavior patterns. If you see them rubbing up against objects (“scratching”), then pull them out right away – if you’d not taken the time to look at them and their habits, you may be too late in catching disease or stress [free, fun & easy].
What else … I can’t really think of anything else off the top of my head. Just make sure that you have simple, small medications lined up for ich, bacterial & fungal infections, and make sure they’re still in date. And ich is sort of like diabetes – it can be caught, treated, and the fish can turn out just fine … or it can wipe out a whole tank.