1. hair algae: it's a phase almost all new tanks have---the phosphate clinging to the live rock serves as fertilizer to algae spores that are just about everywhere on the planet [try having a tank while living on a lake if you wonder about the universality of this stuff!]---cure: best: a refugium; second-best: a phosphate remover. In either case, your cleanup crew will eat it, poo it, and release the phosphate into the water column where it can be gotten out.
2. red slime: it's another phase. It happens..ime, when you have sunlight from a window hitting your tank in a certain spot it will happen there. Improving flow helps; get rid of dead spots. Curtain the window. Best, ime: turn out your lights for 3 days, shield tank from window: 4th day actinic only. Do this once a month. Do not use Red Slime Remover unless you are an older, stronger tank. There is hazard of it weakening your sandbed.
3. flatworms: things that look like little Star Trek emblems. Some say the yellow coris wrasse will eat them; some say a scooter dragonet will; but in this one case, Flatworm Exit is a chemical fix that can be used. The biggest danger with these is their multiplying into such a huge biomass that when you do use FE, it takes out your tank.
4. ich: best: quarantine your new fish, even your first, and be very careful of your specimen sources: ich can ride in on specimen rocks that have been with fish. A medicated dip doesn't hurt with corals: this is species specific, so it makes a difference whether your specimen is zoa or stony coral: read up on it. Inverts: just give them [after acclimation] an intermediate rinse in a second cup of tank water, which will be one dip to try to get any hitchhiking parasite off them.
Best and correct procedure: If ich appears in your quarantine, treat there in qt, with hypo or copper. This is usually successful if you get right on it.
Next best---if ich appears in your main tank: withdraw all fish from your tank and treat together with hypo or copper. NEVER treat with hypo or copper in your main tank. Leaving your main tank with no fish for 6-8 weeks.
Third best: give up. The fish will die. Your other fish will die. Do not get ANY new fish for two full months. Then do what you should have done the first time, set up a quarantine for any new fish. If any of your old guys survived, they'll will pretty well be ich-resistent, and probably---but it's not guaranteed---will never manifest it or host it, so it will die out. If you have survivors, it would be smarter to wait two more months to see if it appears again. If there have been no other outbreaks---you probably won't see it again. But you might, once the new guys go in---if Murphy strikes. So you're back to square one. [You'd be a lot smarter to do it right from the start.] Ich is one of the longest-lasting and most destructive problems a tank can get---and it's one of the easiest to stop, if you do it right---from the start of your tank, meaning your very first fish.
If you have been lucky so far---realize it's luck, which is bound to run out, and start qt'ing new arrivals religiously.
6. Caulerpa or other macroalgae taking your tank: either hope your tank is 75 g, in which case a tang may handle it; or set up a fuge 1/3 the size of your main tank, which will take it out in about 2 months.
7. things keep mysteriously dying. Answer: your water quality is off. Test for: alkalinity, calcium, ph, magnesium, salinity as well as nitrate and ammonia. Answer B: make sure when you acclimate that you are getting within .001 of the same salinity---over the better part of an hour, and simultaneously matching ph. It's likely either your water quality or your acclimation habits.
2. red slime: it's another phase. It happens..ime, when you have sunlight from a window hitting your tank in a certain spot it will happen there. Improving flow helps; get rid of dead spots. Curtain the window. Best, ime: turn out your lights for 3 days, shield tank from window: 4th day actinic only. Do this once a month. Do not use Red Slime Remover unless you are an older, stronger tank. There is hazard of it weakening your sandbed.
3. flatworms: things that look like little Star Trek emblems. Some say the yellow coris wrasse will eat them; some say a scooter dragonet will; but in this one case, Flatworm Exit is a chemical fix that can be used. The biggest danger with these is their multiplying into such a huge biomass that when you do use FE, it takes out your tank.
4. ich: best: quarantine your new fish, even your first, and be very careful of your specimen sources: ich can ride in on specimen rocks that have been with fish. A medicated dip doesn't hurt with corals: this is species specific, so it makes a difference whether your specimen is zoa or stony coral: read up on it. Inverts: just give them [after acclimation] an intermediate rinse in a second cup of tank water, which will be one dip to try to get any hitchhiking parasite off them.
Best and correct procedure: If ich appears in your quarantine, treat there in qt, with hypo or copper. This is usually successful if you get right on it.
Next best---if ich appears in your main tank: withdraw all fish from your tank and treat together with hypo or copper. NEVER treat with hypo or copper in your main tank. Leaving your main tank with no fish for 6-8 weeks.
Third best: give up. The fish will die. Your other fish will die. Do not get ANY new fish for two full months. Then do what you should have done the first time, set up a quarantine for any new fish. If any of your old guys survived, they'll will pretty well be ich-resistent, and probably---but it's not guaranteed---will never manifest it or host it, so it will die out. If you have survivors, it would be smarter to wait two more months to see if it appears again. If there have been no other outbreaks---you probably won't see it again. But you might, once the new guys go in---if Murphy strikes. So you're back to square one. [You'd be a lot smarter to do it right from the start.] Ich is one of the longest-lasting and most destructive problems a tank can get---and it's one of the easiest to stop, if you do it right---from the start of your tank, meaning your very first fish.
If you have been lucky so far---realize it's luck, which is bound to run out, and start qt'ing new arrivals religiously.
6. Caulerpa or other macroalgae taking your tank: either hope your tank is 75 g, in which case a tang may handle it; or set up a fuge 1/3 the size of your main tank, which will take it out in about 2 months.
7. things keep mysteriously dying. Answer: your water quality is off. Test for: alkalinity, calcium, ph, magnesium, salinity as well as nitrate and ammonia. Answer B: make sure when you acclimate that you are getting within .001 of the same salinity---over the better part of an hour, and simultaneously matching ph. It's likely either your water quality or your acclimation habits.