Part I: Preventing Ick
The first topic I would like to cover is preventing Ick.
Marine Ick is what's called on
obligate parasite of fish. The bad news is that its a parasite, meaning that the organism feeds off the flesh of the fish. Ew. The good news for us is that it is an
obligate parasite, meaning that Ick cannot complete its life cycle without a fish host. A diagram of the life cycle can be found
here. The bottom line is: no fish, no Ick. Period. When the Ick organism hatches, it has to find a fish host to feed off of. The Ick organism simply starves to death in quite a short time without a fish.
I don't know who came up with the concept (it wasn't me), but I like to tout the
two lines of defense theory against Ick:
- The First Line of Defense is simply not to introduce Ick into your aquarium.
- The Second Line of Defense is to manage Ick once in your aquarium.
What many hobbyists don't realize is that:
Once the first line of defense is breached, once Ick is introduced to your aquarium, you have no choice but to manage the Ick -- the only sure-fire way to remove Ick from a reef aquarium is to remove all the fish and allow the aquarium to remain fallow for 6-8 weeks. There are many treatment remedies for Ick in a reef system, but most have been demonstrated to simply manage the symptoms of Ick.
You do not need to see Ick spots on a fish for it to be present in your system.
I'd like to point out that this discussion really is geared towards reef aquariums or aquariums with invertebrates. For those with Fish Only systems, you can proceed on to the hyposalinity section.
Not Introducing Ick to the Aquarium:
The only way to ensure your fish never come down with Ick is to make sure you don't ever introduce Ick into your system. And this means quarantine. Any fish you buy or acquire should be assumed to be contaminated with Ick even if you don't see spots. You do not always need to see the spots for the Ick parasite to be present. But how do you quarantine fish if Ick requires fish to complete its lifecycle? Simple. You quarantine your fish in an Ick-hostile environment. Thankfully, fish can survive conditions invertebrates cannot, and what kills invertebrates seems to kill Ick. For example, Ick cannot survive in a hyposaline environment. Even with a fish present, it will simply die. The important thing about quarantine is that you must quarantine for the entire lifecycle of the Ick parasite, which can be 6-8 weeks.
Now, its not enough to simply quarantine all incoming fish. Ick can be introduced to your system on any drop of water; any coral frag, live rock, live sand, macroalgae, hermit crab, snail, anemone, et cetera. Therefore, you need to quarantine every non-fish added to your system as well. Because the Ick hostile environment of the fish quarantine system will kill invertebrates, you may require an entire second quarantine system for everything else. There must be no fish in this second quarantine system. Without a fish being present, even if conditions are otherwise ideal, the Ick cannot complete its lifecycle. The same period of 6-8 weeks must also be used. It may be possible to combine these two quarantine systems, but just use the same system for fish or inverts at different times.
Remember, if you bypass just one drop of water around the first line of defense, you risk blowing the entire effort of quarantine.
Managing Ick in the Aquarium:
Because of the effort involved in quarantine, many hobbyists choose to just manage Ick in their systems. In theory, happy healthy fish should be able to keep Ick in check with their immune systems. Ick is never eradicated from the system. It continues to re-infect. But the fish deals with the infection. Again, just because you don't see a spot doesn't mean Ick isn't there.
Ick can be the canary in the coal mine. If something goes wrong and conditions become sub-optimal, an Ick outbreak may be the first sign you notice. Ick may also not be lethal to fish unless the fish has been weakened. I would be inclined to say that the following conditions all attribute to optimal reef keeping:
- Not overstocking
- Keeping nitrates low
- Preventing temperature and pH fluctuations
- Performing water changes
- Minimizing stress
- Feeding a healthy and balanced diet
- Avoid aggressive fish pairings
- Provide plenty of hiding places
- allow the aquarium to be completely dark at night for several hours
- Maintaining constant salinity
- Making sure your system is established long before adding fish
- Adding fish slowly
I'm sure many people have others to add. The important thing is that once you resign yourself to managing Ick in your system, i.e. your first line of defense has been breached, you kind of have the duty of maintaining a stress free environment in order to prevent fish from becoming stressed.
I hope this provides a framework from which to work more on. I'd like to talk about treatment remedies in the next reply, and I hope people can suggest edits and changes to the above.
Matt