...when things start clouding, closing up, emitting strings of brown gunk, fish start hanging in unusual places, a rash of new creatures are appearing in your tank, and in general, when things are going on that have not gone on before...
..what's the first thing you should do?
1. test the water. Check nitrate, ammonia, temperature, salinity, ph, and alkalinity in that order. Every tank owner should have the alkalinity test and a supply of buffer, imho, no matter what you keep. If you're keeping stony coral or clams, add calcium and magnesium tests to that list. Log your test results and test for the next few days as you try to correct what's going on.
2. If you haven't done a water change this week, do a 10 to 20% water change even if you can't find anything wrong in step 1. Note: a water change will drop your nitrate reading.
3. If you're getting the closing up and brown gunk reaction, or if you have an ammonia reading of any sort or just high nitrates [which can get to an ammonia reading] run some washed carbon for 4 days, then remove it and toss. Carbon can remove a lot of things, including ammonia and the irritants some soft corals spit at each other. Always toss carbon after its expiration period: over-charged, it can start releasing everything it just absorbed.
4. if you've got cloudy water, it is oxygen-poor, just because it is cloudy: be very attentive to your fish and have your qt filled with clean water and standing by. Any time you suspect there is not enough oxygen in your tank, have that quarantine tank ready for your fish. Corals tend to just close up and wait: in that sense they're tougher than fish. To solve your cloudiness problem check for:
1. dying caulerpa mass. That is serious. Get all specimens to clean water. Tank crash in progress. Get on RC and ask for help, while doing a big water change and running carbon.
2. sandbed disturbance: serious: get a one micron filter [cannister] or a diatom filter and run it immediately until clear. Never overturn a sandbed. Noxious biochemicals get released. They're safe, if kept where they are: not safe if released into your water.
3. just dust: will settle, but may irritate specimens. A one micron filter or even filter sock will fix this. Personally I don't run filter socks longterm, just for immediate need.
4. kalk accident or adding calcium and buffer together can do this: it will clear on its own, but watch your ph. If your ph spikes, add a tiny bit of club soda, but I mean tiny, and test every 15 minutes. Remember that it will be falling fast on its own, so don't compound your problem by overdosing in the other direction.
HTH.
..what's the first thing you should do?
1. test the water. Check nitrate, ammonia, temperature, salinity, ph, and alkalinity in that order. Every tank owner should have the alkalinity test and a supply of buffer, imho, no matter what you keep. If you're keeping stony coral or clams, add calcium and magnesium tests to that list. Log your test results and test for the next few days as you try to correct what's going on.
2. If you haven't done a water change this week, do a 10 to 20% water change even if you can't find anything wrong in step 1. Note: a water change will drop your nitrate reading.
3. If you're getting the closing up and brown gunk reaction, or if you have an ammonia reading of any sort or just high nitrates [which can get to an ammonia reading] run some washed carbon for 4 days, then remove it and toss. Carbon can remove a lot of things, including ammonia and the irritants some soft corals spit at each other. Always toss carbon after its expiration period: over-charged, it can start releasing everything it just absorbed.
4. if you've got cloudy water, it is oxygen-poor, just because it is cloudy: be very attentive to your fish and have your qt filled with clean water and standing by. Any time you suspect there is not enough oxygen in your tank, have that quarantine tank ready for your fish. Corals tend to just close up and wait: in that sense they're tougher than fish. To solve your cloudiness problem check for:
1. dying caulerpa mass. That is serious. Get all specimens to clean water. Tank crash in progress. Get on RC and ask for help, while doing a big water change and running carbon.
2. sandbed disturbance: serious: get a one micron filter [cannister] or a diatom filter and run it immediately until clear. Never overturn a sandbed. Noxious biochemicals get released. They're safe, if kept where they are: not safe if released into your water.
3. just dust: will settle, but may irritate specimens. A one micron filter or even filter sock will fix this. Personally I don't run filter socks longterm, just for immediate need.
4. kalk accident or adding calcium and buffer together can do this: it will clear on its own, but watch your ph. If your ph spikes, add a tiny bit of club soda, but I mean tiny, and test every 15 minutes. Remember that it will be falling fast on its own, so don't compound your problem by overdosing in the other direction.
HTH.
My poor skimmer pump runs, that's what I can say about it, my system has never seen a filter sock, and the salt creep layer in my jump-prevention downflow top could supply a tank. [It's not where it could fall in and hit a specimen.] 
