UV Question

leewish · Apr 14, 2021

I know that UV can only handle the free swimmers of ich and is used more for management but would this situation potentially eradicate it?

Currently I have fish in a 27g tote waiting to introduce multiple tangs in multiple totes together into display. No treatment is going on but I did get the replacement parts for my 25w Aqua UV fixed and decided to leak test it on one of the totes. So if I am running the flow properly for this size UV (400gph) could a well oversized UV like this for roughly 20-25 gallons of water in it actually eradicate ich as long is I leave it running long enough in the tote?

Jay Hemdal · Apr 14, 2021

leewish said:
I know that UV can only handle the free swimmers of ich and is used more for management but would this situation potentially eradicate it?

Currently I have fish in a 27g tote waiting to introduce multiple tangs in multiple totes together into display. No treatment is going on but I did get the replacement parts for my 25w Aqua UV fixed and decided to leak test it on one of the totes. So if I am running the flow properly for this size UV (400gph) could a well oversized UV like this for roughly 20-25 gallons of water in it actually eradicate ich as long is I leave it running long enough in the tote?

The normal opinion is that UV on a side stream cannot eradicate protozoan parasites. They do work when working in a flow through symptom where water is 100% irradiated as it moves from one tank to another in a system.
Side stream doesn’t work due to dwell time. Enough of the water escapes passing through the sterilizer, that the parasite population never really hits zero. These units CAN quell minor to moderate infections though.
Also, think of the life cycle of ich and velvet as sort of a “guide”, there is some thought, especially with velvet, that the theronts can live, stuck in the fish’s gills, and thus never get exposed to the UV. That is why UV doesn’t work for Brooklynelka, Uronema or flukes.
Jay

Bpfor3 · Apr 14, 2021

My experience is that UV cannot eradicate it. I had an outbreak of ich after it snuck into my system on a frag. i have several tangs that had it. Tried to ride it out with good food, water quality, etc. Even dosed peroxide for a while. Continued to get worse. Stuck a 150 watt pentair sterlizer on my tank, which is 150 gallons. Intake pump correctly sized for protozoa eradication and put on the sand bed in my tank. Left it running for 6-8 weeks. No ich. Got brave and turned the UV light off and kept the flow going. Within a week saw a spot, which turned into a few more, until i got uncomfortable and turned the UV back on again. No spots. So while the UV definitely knocks the ich back to nothing, something is still getting through and popping up when i shut it down.

A 150 watt UV is almost 6 feet long and is more than enough to do the job on my system.

Malcontent · Apr 14, 2021

I think it's possible. The UV isn't the only thing killing ich. The fishes' immune systems contribute as well. A certain population size will be required to keep the infection going but each generation gets whittled down by UV and natural causes of death until there isn't enough to sustain the population. It isn't necessary for UV to kill every theront and on the first pass.

Six to eight weeks might not be long enough to eliminate ich. The pattern I see (in freshwater) is a spot or two and occasional flashing after adding a new fish. Then it goes away and maybe returns a few weeks later. It becomes less severe and less frequent as time passes (unless I add a new fish and restart the cycle). Months or years after the last new fish, the ich is probably long dead. Even very stressful events such as moving cross country don't result in an outbreak.

threebuoys · Apr 14, 2021

I agree with Jay. I do believe UV will kill the theronts which pass through the canister. I also believe a high speed flow is better than a slow speed (some will dispute this) because the UV effect is cumulative to the protozoan and very effective for fast replicating bacteria in the water column. High speed can turn over the volume of water five, ten, or more times per hour which is faster than the reproductive rate of many of the problem bacteria, and cumulatively more than the dosage required for the theront.

But any theront that does not pass through the filter may infect a fish to continue the life cycle. Some protomonts may be sucked through the UV also, but any that make it to a hard surface will attach to form the tomont with a longer incubation period. One tomont can hatch 200 + tomites which become theronts.

Perhaps over an extended period each stage of the life cycle can be eliminated, but there is no way to know for a fact that has occurred.

Nonetheless, I think the UV offers advantages in case crypto does exist, and as a deterrent to bacteria and algae in the water column.