[FishyFishy89]

I saw some canister filters with these UV sterilizer bulbs. They claim the bulbs kill algae spores, bacteria and promotes clearer water. My questions:
1) does it REALLY kill algae?
2) what bacteria does it kill? Tanks DO need some sort of bacteria, so I don't want the good stuff getting killed off.

Thanks!

 

[jaysee]

UV sterilizers do work. However, contact time with the bulb is what determines the level of effectiveness. The more complex something is, the more time with the bulb is required to kill it. Algae is not complex at all, so the UV sterilizer in a canister filter might take care of that. Parasites are much more complex, so they need more time (a slower flow rate). For a UV to be most effective, it requires a very low flow rate - on the order of 50 GPH. The flow rates with canisters are far too great to do anything but battle green water, if they can even do that.

 

[funkman262]

Jaysee is correct on the contact time being key for effectiveness. As far as killing beneficial bacteria, those are more concentrated in the filter media than in the water column so that wouldn't be much of an issue.

 

[FishyFishy89]

I understand BB is in the media, I'm unaware if the UV light has direct contact with the media. I would hope they actually separate the two.

I honestly wouldn't mind giving it an actual test as to wither or not it helps to kill of algae. I believe I have hair/diatoms bugging my plants. It could be a nice fix to use while I slowly fill the tank with plants.

 

[funkman262]

I doubt it would do anything to algae already fixed in the tank. Keep in mind that it can only kill what actually comes into contact with the bulb. As you said, it can kill algae "spores". I've used it for green water and it worked really well for that application.

 

[FishyFishy89]

It would prevent more growing yes? If so, it could still potentially help control the algae population?

 

[jaysee]

The UV bulb is built into the head (top) of the filter. The incoming water flows over the bulb on its way to the bottom of the filter body, where it is then pulled up through the layers of media. It is not in contact with any other media.

 

[Sanguinefox]

Isn't this just one of those things where it can help with something but isn't really a cure? It's like, if you have a problem with green water, you find the source, eliminate the variables and done.

If you get a UV sterilizer all it really does is offer a quick fix and you are screwed once it stops working if you didn't fix the initial problem. I hear some people use this on fry tank set ups though to help with the overall batch but ...I don't know how true that is.

 

[FishyFishy89]

I know it's not a complete fix. I've limited my lighting as much as I could(I have live plants), completely removed my liquid ferts and I'm adding more plants when I can. I believe more plants would compete with the nutrients the algae needs and the algae would then just die off. I noticed I've been removing less and less algae each week.

 

[jaysee]

Isn't this just one of those things where it can help with something but isn't really a cure? It's like, if you have a problem with green water, you find the source, eliminate the variables and done.

If you get a UV sterilizer all it really does is offer a quick fix and you are screwed once it stops working if you didn't fix the initial problem. I hear some people use this on fry tank set ups though to help with the overall batch but ...I don't know how true that is.

Not all imbalance are permanent. For instance, a tank could receive too much direct sunlight, but only in the summer. But in general, I agree, it's not really needed - many a fish tank gets along just fine without it.

 

[JDM]

The UV bulb is built into the head (top) of the filter. The incoming water flows over the bulb on its way to the bottom of the filter body, where it is then pulled up through the layers of media. It is not in contact with any other media.

Most things have been mentioned already, contact time, water flow rate, one more thing to need to replace when it fails is another point. I'll just do my usual rambling.

If these are in the flow before the media (which I believe is the case as Jaysee pointed out) then this compounds the issues with these setups as the water is not already clear. The UV relies on direct light exposure and particles (turbidity) will shade the water that is not directly against the bulb or lens. Any UV system puts the light exposure as the very last point before use. I expect that tannic water will almost nullify most UV treatment altogether even before turbidity comes into play, but that is just a logical assumption.

I had a few paragraphs more but I deleted them, too much information. If anyone really wants it, pm me.

Jeff.