Emergency Procedures -
Ammonia / Nitrites are too high
1 Change water - several times if needed - 75% or more each time
Your problem is not enough good bacteria and/or overfeeding or decaying organic matter
Your main pump shuts off
Using powerheads, keep the surface of the water moving. This can provide all the oxygen for the tank indefinitely.
Your problem is either an old pump died from old age or you haven't been doing regular pump maintenance. Pumps should be cleaned at least 4 times per year.
You ran out of DI water and you're pump is running dry
1 If you have an adjustable overflow elbow like we use in our setups, you can lower it to a horizontal position and let the level of your tank drop.
Your problem is lack of attention to your system, poor planning and not having enough water on hand or you need an automatic top-off system.
You have a fish that's a bully.
If you can catch him easily. Put him in a large net and him let sit there until the lights go out. Then let him go. The "fish jail" often mellows them out. Be sure to put a small rock in the net so the fish doesn't get tangled. Remove the rock before letting the fish go.
If it's a real problem catching him. You can keep him in the net until you have a better home or put him in your sump if you have one.
Your child pours something in your tank.
1 Change water. 90% or more 3 or more times. Use tap water if necessary. Speed is essential. The temperature only needs to be close. De-chlorinators are not needed. They are in the salt mix already. This is one reason to maintain a supply of salt at home if your are buying our saltwater.