Tropical Fish Hobbyist - November 2007

Is an Ounce of
Prevention Worth
a Pound of Cure?

Many of the professional aquarists I’ve talked to over the years go a step further, routinely medicating quarantined fish for a host of diseases, even if there’s no evidence those diseases are present. Some also give new freshwater fish a salt dip, and new marine fish a freshwater dip, to kill off parasites before placing them in quarantine.

But that’s not something most home aquarists should be doing for several reasons, and Miller-Morgan and Noga agree. First, both pointed out that professionals usually use medications based on an in-depth knowledge of both the species they’re dealing with and the kind of pathogens that species is prone to; they also understand the impact of medications on both organisms. Home aquarists, however, rarely have that kind of knowledge.

In addition, adding medications to tank water is in itself a stressor to fish because it changes the concentration of dissolved solids in the water, which in turn affects the fish’s osmoregulatory processes.

And lastly, said Miller-Morgan, treating for diseases the fish may not have can ultimately lead to medication-resistant pathogens, which can create a much bigger problem down the line.

Quarantine Basics

So what would a good quarantine system look like? The size of the tank will vary according to the sorts of fish you keep— larger or fast-swimming fish, for instance, require larger quarantine tanks than smaller, quieter fish. But beyond that, simpler is better; keep the lighting low—it keeps fish calmer—and make sure that anything you put into the tank is easily sterilized.

That means opting for things like plastic plants and PVC pipe (added not to make the tank look beautiful, but to make the fish feel secure) over real or silk plants. “And nothing porous, like lava rock, because pathogens can get into the pores,” Miller-Morgan said. He also recommends skipping the substrate, since a barebottom tank is easier to keep clean and also to sterilize later. And, he adds, make sure that any nets and siphons used in a quarantine system are kept separate; using them in an established tank is a good way to spread pathogens.

The only “problem” that has to be addressed with any tank that isn’t in

constant use is how to keep the biofilter going. Some people keep a few fish in them, transferring them to their main tank when the quarantine tank is needed for new arrivals. You can also keep the biofilters running in a fish-free quarantine tank by adding small amounts of ammonia.

Personally, I keep my quarantine tanks empty between use; when I need them, I instant-cycle them by pulling filter pads from my established tanks and putting them into the quarantine-tank filters. (Alternatively, you can keep an extra box filter running in an established tank, ready to move to a quarantine tank when needed.)

If you need to sterilize a quarantine tank, Miller-Morgan says that bleach, at a concentration of 200 ppm (or 200 mg/liter of water), will do a great job. However, he cautions, organics do cause bleach to break down, so make sure you rinse everything thoroughly before using the bleach, or it won’t be as effective.

Back to the Beginning

To close this month’s column, I thought I’d return to the saga of my nephew and his county-fair goldfish.

I’d like to be able to tell you that Aunt Laura’s wisdom prevailed that evening at the fair, and that I managed to talk him (or rather, his parents) into stopping at the local pet shop for a quarantine tank on the way home. I did not.

Rather, the fish went directly into my nephew’s 30-gallon goldfish tank along with his three established fish (although I did manage to work in a lesson on acclimation techniques). I did, however, suggest to my brother that he do a series of partial water changes over the course of the next week to reduce any free-swimming parasites that might be in the water.

As I write this, several weeks have passed and so far neither the new fish nor the originals are showing any signs of a problem. So my nephew could well be lucky.

But I also know that good luck rarely lasts forever, and if Ben is serious about fishkeeping, which he seems to be, there will be many finned additions to his collection in the years to come.