Tank emergencies happen to the best of us. No matter how careful we are, you just never know when something unforeseen will happen, be it a heater breaking in your tank and contaminating your tank with copper, a pump cracking internally and giving you copper contamination, or a foreign substance being introduced to your tank (pesticides are a common problem, but many common cleaning products have chemicals in them that could be lethal to your tank’s inhabitants). Of course, whatever calamities you have prepared for, there are always others you can’t even imagine. So, with this in mind, here are some items that are good to have on hand at all times to better help prepare for the unknown.

• Carbon. Lots of it. And something to contain it. It can be a hang-on-the-back filter, an old canister filter, just some media bags, a filter sock, a Phosban Reactor, or what have you. Activated carbon is great for removing contaminants from your tank’s water, and can be a real life saver in a pinch.
• PolyFilter pads. Preferably more than one. Similar to carbon in its ability to remove contaminants, but it’s far better at removing copper from water than carbon is. (This is my opinion only, not based on any scientific research.)
• Enough RO/DI water on hand for a large water change is a luxury for some, a necessity others wouldn’t even consider doing without. Find a workable way to have as much as possible on hand in case of an emergency. You can’t rely on your local fish store to be open at 3AM on a Sunday morning, which is inevitably when most emergencies happen! Obviously, having this water already mixed with salt is preferable. One option is to mix up the water for your regularly scheduled water change, and after your water change, immediately mix up a new batch of water, and just let it aerate on standby until it’s time for your next water change. That way you’ve almost always got some fresh water on hand and ready to go.
• Pumps and hose to move water out of and into your tank.
• Having a quarantine system already up and running can be a lifesaver - literally! In an emergency, you can move your most prized livestock out of the troubled main system and into your running quarantine system in a pinch, removing at least those specimens from the sick main tank.
• Having some small containers with lids that you can take and set aside water samples in would be a good idea. That way, once the panic is over and things have stabilized, you have a water sample from when things were at their worst for testing and analysis so you can try and figure out what exactly was going on.
• Prime. In a pinch, it can be used to de-chlorinate tap water if RO/DI is unavailable. RO/DI is always preferable to tap water, but in an emergency you have to think in triage mode and do as much as you can, as fast as you can to remove whatever is causing the problems, and tap water can be preferable to poison! It can also bind toxic ammonia if ammonia is part of (or a result of) the problem your tank is experiencing.
• A battery-operated air pump (with tubing and airstone!) can be indispensible during a power failure, as well as for keeping specimens alive in a separate tank for segregation or transportation if that becomes necessary.
• Foam insulation padding - the pink boards we put under the tanks to balance them. In a power outage in cold weather, these can be placed around your tank to help preserve its warmth. In a pinch, you can wrap your tank in blankets too.
• Keeping some plastic bottles (2 Liter coke bottles, or ever 20 oz coke bottles - well cleaned!) filled with RO/DI water in your freezer can be helpful as well. If the power fails during the summer (or if your power is on, but your air conditioning fails), these can be removed from the freezer, cut open and the blocks of RO/DI ice can be put in your tank or sump to help keep the temperature down.
• The phone number of a good buddy who also keeps a reef, so they’ll understand when you call them at 2 in the morning needing help. Even if they don’t have any supplies to help, having another person with you, or at least talking to you on the phone, can really help; both with giving you advice, and keeping you from doing anything drastic that could cause more harm than good.