There are two basic types of emergencies: outbreaks and tank crashes. An outbreak refers to a wide spread problems with disease or parasites that threaten the entire tank. A tank crash is when the aquarium chemistry falls into a vicious cycle. While an outbreak can cause a tank crash if you leave the dead organic material in the tank, we will treat them as separate phenomena.

Disease Outbreak

Multiple fish or corals suffering from a similar disease is an outbreak. An outbreak can wipe out all fish or corals quickly or may ramp up slowly and affect only specific more susceptible species. Calling an outbreak an emergency is relative to how fast it is progressing. Like a tank crash, the major option to consider is whether to remove the fish (or affected corals) from the main system. This is not always the best option however as some diseases may be treated within the system. There is also the possibility that removing the fish from the system may be impossible.  If you choose to keep your fish/coral in the tank and attempt treat the disease, first review see if you recognize any of the common symptoms and then return to the subsequent steps for disease assessment and treatment.  

Tanks Crash

  • Usually the result of equipment failure or aquarium neglect (overfeeding, insufficient water changes, failure to remove dead or dying organisms). This results in
  • The build up of organic waste. This causes fish to either get sick from the toxicity or from opportunistic infections from being immunocompromised.
  • If an outbreak leads to a substantial amount of dead organisms that are not soon removed from the aquarium, this can initiate a tank crash
    • Organic wastes may surge to toxic levels.
  • Microorganisms that break down this waste can surge in population and activity which may then consume all of the oxygen and cause a worse problem of anaerobic conditions in parts of or the entire tank.
  • As the microogranisms convert ammonia into Nitrite, this uses up the carbonate ion the water, causing a depletion in buffer which may cause abrupt pH changes

How to recognize it

  • Increased ammonia or nitrite (should never be present in an established tank
  • Decreased KH and pH.
  • All fish on bottom or at surface gasping.
  • Corals deflated or bleaching out. Some corals may even be dissolving.

What to do -

  • First, if possible, remove the fish to a clean system. Ideally a quarantine tank which is already set up but this can even be a large Tupperware bin with an airstone. Acclimate them to brand new water and try to get one healthy rock or a some filter material to keep somewhat of a biological filter going to try to keep wastes (ammonia/nitrite) down. Bacteria on the rock or in the sponge will eat fish waste. You can use an ammonia binding agent (prime or Amquel) and an ammonia alert badge or API ammonia test kit (both of these are salicylate based and monitor/test free ammonia NH3 not total ammonia (NH3 plus NH4+ which is the bound form)

  • Next, get the dying and dead stuff out of the main tank. You can siphon (gravel vacuum) a large portion of the substrate (up to 50% each day in a critical system). Read about siphoning in the tank maintenance section.

  • You can do substantial daily water changes (up to 80%) to return water quality to survivable parameters.

  • It is important to do this slowly. Make sure not to expose animals to more than a 50% change each hour.

    • Remember things may continue to die for days or weeks after exposure to bad water for any amount of time.

    • You can do these daily until you see the animals behaving normally. Try to cater the amount of water you change out daily to the urgency of the water change based on the appearance of the animals themselves and the water quality (see previous section on when things aren't critical).

    • For example, if you have a 100 gallon tank and you take 80 gallons out, you have 20 gallons left. Now, do not add more than 10 gallons to this tank over the first hour (50% of 20 is 10). For the second hour, when you have thirty gallons, do not add more than 15 gallons over the course of that second hour (50% of 30 is 15).

The use of chemicals to bind toxic biological waste products ( primarily ammonia and nitrite) is a good option along with and after water changes

  • Purigen by Seachem will bind ammonia, organic molecules which lead to phosphates, and all the hair spray/bug spray/sun tan lotion that humans don't realize gets into tanks in the same way as activated carbon but Purigen has a higher capacity and is rechargeable with bleach. It is somewhat expensive initially but works well for a long term. You know it is used up when it turns light brown.

  • Water conditioners which break up chloramine and bind ammonia (Prime by Seachem and Amquel) in tap water can be used to control ammonia.