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Discussion Starter · #1 · (Edited)
I've recently added UV sterilization equipment to my 100 g planted tank with fish and inverts, and I thought it might be useful to post my account.

I recently moved, and had to completely tear down my tank in the process. Details:
100 g 25-27 degrees c
CO2 injection ~30 ppm (this alone results in pH 6.5)
(recently) Sodium Bicarb to pH7
Calcium Sulphate, Magnesium Sulphate, Potassium, traces
350W cfl 6500K lights
UGF+OHF
Fish before the move: 11 SAE's , 90 neon tetras
Nerite snails, hundreds of cleaner shrimp
Lots of plants (swords, anubius, water lily, java fern) making sort of a dense canopy

I put the tank back up in my new place, and had to leave town for a week on another matter and left the care of the tank to a friend, who then killed all my SAE's, presumably by overfeeding. They had been quite healthy before the move, and losing them was a real shock.
Thorough cleaning, 50% water change, things started to get back to normal.
Then the tetras started to die. I was down to about 20 before that stabilized, raising the pH a bit seemed to help which is odd for tetras, which are supposed to be a low pH fish. I had never lost any tetras before, they were quite healthy in the past. No signs of anything, they would just dive to the gravel, flop around a bit, then die very quickly, one by one.

I added a dozen more very small SAE's. They've been great ever since, really growing fast.

I added 6 cheap angelfish, all dead in a week.

A week later, added 40 more neon tetras. They started dying again a couple days later, but only a few this time.

Added 5 pearl gouramis, they're fine. They eat a lot, have taken up some real nice color, very active.

A few days later, after the gouramis acclimated, I added 7 black tetras. 4 BT's were dead the next day, and the remaining ones, horror of horrors, had ich.
It took me 3 days to get 2 generic 5W UV sterilizers, by which time a few of the gouramis had a few white spots, and a few more of the neon tetras died. Set up the UV's to do 60 g/hr each, or 12 g per watt-hour. I was skeptical, but really couldn't risk chemical treatment killing the nerite snails and cleaner shrimp, it would be a disaster. Have you ever tried to quarantine 60 neon tetras from a planted tank, or hundreds of cleaner shrimp?

Results:
After 2 weeks of running the UV sterilizers, I haven't lost one fish. The 3 remaining BT's recovered.
The gouramis lost their white spots. None of the neons or SAE's contracted ich.
One observation I made is that one of the gouramis, which had gone unscathed, developed a small white spot near its dorsal fin the day I started the UV. It was definitely the parasite, not a piece of food or a bubble. It was still there when I fed them that evening, but it was gone by morning.

Now, UV sterilization isn't supposed to treat the fish. It can't. It can only treat what's in the water column that passes through the sterilizer itself. This is what I was hoping for, the gradual removal of the free-swimming stage of ich, resulting in more of an ich-control. Complete elimination of ich seemed a bit optimistic.
I hold a degree in biology + chemistry, and a lot of the reading I did on the web about UV sterilization and redox potential seemed more like pseudo-science to me, and contradictory in many aspects. All my money was on just the sterilization of the water, and hoping to remove the great majority of the free parasites from the water.
However, observation seems to indicate that the fish developed the resistance to fight off the infection, reducing the duration of white spots from an expected week or more to less than a day. The last white spot I saw was a week ago, or 1 week after starting the UV treatment.
2 weeks, no dead fish.
I'll continue the UV for another 2 weeks, then wait and see.

For the interested, http://www.americanaquariumproducts.com/Redox_Potential.html, a lengthy article about UV irradiation and redox potential in the aquarium. Don't blame me if some of it sounds like pseudo-science. Marketing is not your friend.

Conclusion: Much better than expected. I was skeptical but desperate when I decided on UV, and the best I had hoped for was keeping the white spot under control while I worked up plan B. However, white spot **APPEARS** to be eradicated. Further observation is required to confirm this.
It appears there may be some validity to the (dubious)claims that UV treatment, via redox potential, is an immunity and health booster for fish. As of now, everything looks top-notch.

Final count:
60-70 neon tetras
3 black tetras
12 SAE's
5 pearl gouramis
nerite snails (10-13)
cleaner shrimp (100--200)
 

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I'm sorry about your losses and so glad your fish are better. Do you plan to leave the UV running all of the time, or just when there is a problem? I was going to plumb mine in semi-permanently, but haven't gotten around to it. I seldom have problems, yet I wonder if it would be beneficial.
 

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Discussion Starter · #3 ·
I'm conflicted. Aesthetically, it would be better without them. However, there's conflicting information regarding the ongoing benefits of UV. The old school seems to think it will wipe out microorganisms in the water water column that would normally carry out a low-grade attack on your fish, thus keeping their immune systems on guard, much like a vaccination that keeps your fish equally prepared for the real nasty stuff. Removing these microrganisms by UV would thus weaken your fish to microorganisms they aren't normally exposed to. This school of thought wisely advocates water changes, sanitation, water parameters, etc.

The other school of thought proposes that UV, through reduction/oxidation, destroys non-living organic radicals in the water column that poison fish and weaken them. Furthermore, (this is where it starts sounding a bit pseudo-scientific), calcium, magnesium, carbonate, and trace metals are kept in a chemically excited state when exposed to UVC, which provides a hostile environment for microrganisms, while stimulating mucous secretion and immune response in the fish.

While I'm not completely bought into that, it does appear my fish are healthier than ever. My SAE's have beautiful iridescent green markings, the black tetras' fins , which were a ragged mess, healed up very quickly, the pearl gouramis are dark and lustrous, the neon tetras are getting their little white "trigger fins" they get when they are really healthy. Even the snails, which I would often see "sleeping" (maybe sick?) are constantly on the move. I never see those guys rest anymore.

Maybe in 2 weeks I'll take one out and leave the other one in? I guess I was hoping to get feedback that would answer your question as well.
 

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Discussion Starter · #4 · (Edited)
To liven things up, here are some pics.

Pic 1
5 watt UV sterilizer. As you can see, it's not a pleasant addition. There's another one on the other side.

Pic2
My pearl gouramis, a male (top) and a female. They love the plants. They get dark as storm clouds during the feeding frenzy!

Pic3
This guy never takes a break.

Pic4
Jungleland. See why I didn't want to chemically treat? Could you imagine?

Pic5
How many cleaner shrimp can you find? I see 4 , possibly 5.
 

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