Pszemol wrote:

Could you give me more details?

I started keeping marine fish in 1975. Those were the days of the undergravel
filter, and the use of powerheads was hailed as a great advance by my friends
the next year. I started out with a 10 gallon tank and could keep one or two
fish alive with a great deal of effort. In 1977, I scored a great deal on a used
100 gallon tank. In the early 90s, I swapped for the 125 I have today. Until
last year, everything was fish-only with a variety of filtration methods. I did
not set up a hospital tank until last year when I started adding live rock.

I first added a UV sterilizer to my tank about 1977 or '78. It was an 8 watt
unit. In the early '90s, I added another. In 2005, I went back to an 8 watt unit.

Without a hospital tank, adding a new fish was always hazardous. Back when I had
no UV on the tank, once one of the fish started showing signs, the life
expectancy of that fish was usually less than 3 days; they could not take the
combined stress of the parasites and the copper treatment. Other fish in the
tank would invariably show signs of infestation later, but would usually make it
through. Once the first sterilizer was added, the rate at which the disease
spread decreased; my theory is that some of the parasites were being killed in
their free-swimming stage. After that, the first fish to show signs usually
survived, and some of the other fish would never show any signs at all.

Once I added the second sterilizer, I never lost a fish to ich, though I did get
the occasional infestation. In short, there was a direct relationship to the
number of watts of UV and the intensity and rate of spread of the disease.

Since I was not religious in changing the bulbs (and the bulbs get less
effective with time), I was also in a position to notice that an outbreak was
worse when the sterilizer bulb was pretty old. Again, this didn't happen once I
had two units running.

Since I've moved in the direction of a reef tank, I no longer have one hooked up
to the main tank. At the moment, my hospital tank is housing my cichlids while I
renovate their bedroom, but my remaining UV will go on the hospital tank once I
set that back up.

George Patterson
If you torture the data long enough, eventually it will confess
to anything.