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Discussion Starter · #1 ·
I have done a ton of research on this but haven't been able to figure out how much dwell time is too much. I stumbled upon a couple of great deals, a Penn plax 700 canister for $50 and an 18 watt coralife turbo twist for $60. The turbo twist recommends min 200 max 400 gph but the penn plax is rated at 185gph so will be lower with media. Would that much dwell time have negative effects on the water? Or would it actually be more effective...any educated answers would be appreciated!
 

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From what I've read here on the site, slower is better. It doesn't seem like too much dwell time would hurt anything; however, you want your system to be efficient also. I'd error a little on the slow side if I was to purchase a UV system.
 

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Discussion Starter · #3 ·
Thanks for the response. Yeah I've gathered the same from what I've read just wasn't sure if there is too slow. Forgot where I read it but someone had a theory too much dwell time could almost like bleach the water...no hard facts. Still got me wondering though
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All of the "sterilizing" systems kind of scare me. Were I to purchase one, it would be for use in an as needed basis as an option to chemicals. My setups are very simple, so take that into account.
 

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I can't think of a reason to have one in the first place to be honest.

They seem like only a solution to a symptom and not the solution to a problem. Pathogens shouldn't be entering a tank, except by new fish but they should be quarantined anyways.

As for green water, that's a too much light issue usually, but I suppose if the only possible place for a tank was somewhere in direct sunlight you may have to, but I still think you'd end up with other algae issues.
 

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I also think there's no such thing as too much dwell time while too little to kill parasites and/or algae would make it pointless to use.

As already mentioned, the use of a UV sterilizer is considered by many members to be unnecessary and considering the numbers of successful tanks running w/o a UV sterilizer, it's hard to disagree.
 

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Discussion Starter · #7 ·
I agree, I've never used one but I'm setting up a tank with an electric blue jack dempsey and I've heard they do them wonders. Plus can't beat the price. Thanks for the opinions.
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too much dwell time in a uv... not heard of that one, I couldn't possibly see any ill effects coming from this even in a planted system. I would advocate the use of a UV light if you have the money to spend on them. I look at them as a added insurance along with weekly w/c's. some people swear by them some people say they are useless but if setup correctly flow rate/wattage their results show for themselves.

I wouldn't use a uv to treat a issue usually but more as a prevention. when I was looking into getting one I was recommended a 30 something watt with like 90 gph flow. even with a higher watt you would want your flow under 100 gph IMO - you get better uv effectiveness.
 

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Wattage and flow rates are directly related - The lower the wattage, the lower the flow (more dwell time), the higher the wattage the higher the flow (less dwell time). 30 watts is pretty high for a UV filter, so while one could pair that with a low flow pump, the things aren't going to get any deader by spending the extra time in front of the bulb.
 

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so a 3w bulb has the same intensity as say a 30 watt?

a low flow/low waatt bulb is generally seen in uv's that are more focused towards green water while the higher end sterilizing ones are higher wattage and can have a higher flow. "dwell time" or I would rather call it exposure time im sure directly reflects how good of a performance you are getting along with how big /higher the wattage is.

ive heard of a guy getting gram neg filtration with a 30 watt at like 90 gph... never heard of such filtration at lower wattage then that unless the water was maybe trickling through...
 

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so a 3w bulb has the same intensity as say a 30 watt?

a low flow/low waatt bulb is generally seen in uv's that are more focused towards green water while the higher end sterilizing ones are higher wattage and can have a higher flow. "dwell time" or I would rather call it exposure time im sure directly reflects how good of a performance you are getting along with how big /higher the wattage is.

ive heard of a guy getting gram neg filtration with a 30 watt at like 90 gph... never heard of such filtration at lower wattage then that unless the water was maybe trickling through...
No, a 3 watt bulb and a 30 watt bulb do not have the same intensity - that was the point I was making. Because a 3 watt bulb is weak, the amount of exposure time needs to be high because it will take longer to kill something. A 30 watt bulb is powerful, so it will kill things quickly and so a shorter exposure time is necessary. Of course one can have a prolonged exposure time with a high wattage bulb, but like I said it doesn't make things any deader. And of course a high flow with a low wattage bulb renders it useless.

I've spent an embarrassingly massive amount of time on forums and I've never heard of gram negative filtration. I assume you mean his UV kills gram negative bacteria? That would be expected from a 30 watt bulb, as that's quite powerful. But that doesn't mean that a lower wattage bulb doesn't as well, under the right conditions. I'd like to know how this guy determined he had "gram negative filtration".


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I'm on the UV being unnecessary side.

The higher the wattage the longer the bulb which allows for longer exposure. The intensity at any point along the bulb may be the same between a 3or 30 watt so the length of the bulb given identical flow rates would lead to a longer exposure, not necessarily a more intense exposure. Because UV light is harmful I think they are restricted to certain intensities for residential use. But don't quote me on that.

Jeff.
 

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No, a 3 watt bulb and a 30 watt bulb do not have the same intensity - that was the point I was making. Because a 3 watt bulb is weak, the amount of exposure time needs to be high because it will take longer to kill something. A 30 watt bulb is powerful, so it will kill things quickly and so a shorter exposure time is necessary. Of course one can have a prolonged exposure time with a high wattage bulb, but like I said it doesn't make things any deader. And of course a high flow with a low wattage bulb renders it useless.

I've spent an embarrassingly massive amount of time on forums and I've never heard of gram negative filtration. I assume you mean his UV kills gram negative bacteria? That would be expected from a 30 watt bulb, as that's quite powerful. But that doesn't mean that a lower wattage bulb doesn't as well, under the right conditions. I'd like to know how this guy determined he had "gram negative filtration".


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http://www.tropicalfishkeeping.com/...nternal-uv-filter-recomendation-149713/page3/

reply #23 I believe
 

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Well, reply #24 - that is one mention. I never went back to the thread so I missed it :dunno:

I'm not commenting on whether he did or did not, because I don't know enough about the story to have an opinion. But just because someone says something on the internet doesn't mean it's true. Doesn't mean that they are a liar, either. If anyone wants to do research on this matter, I hope that they do and that they come back here and share it with us, so that we may understand these things just a little better.
 

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Gram negative bacteria is just a classification of the bacteria based on a staining method called the Gram stain. E coli I think is an example of a gram negative bacteria. You hear this talked about in ceramic filtration but whether it's gram positive or negative in that case makes little difference as it has to do with the size of the bacterium and filter media pore size, not how thick or tough the cell wall of the critter is.

Unless he could identify the bacteria visually or culture them to administer the stain test, perhaps he had an outbreak with very specific set of symptoms that point to a particular strain of bacteria and it couldn't have been anything else....

Mitch, your water issue cleared before you bought a UV unit, didn't it?

Jeff.
 
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