Final Word on UV Sterilisers

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flanque

Aquarium Advice FINatic
Joined
Jun 9, 2004
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740
Okay after reading all the information I can find online and on this forum, I am 95% convinced to get a UV steriliser. I have only one question...

I now believe that a lot of oxidising bacteria lives on the rock and I could even run an aquarium without bioballs, etc in the filter, but my question is about free floating bacteria.

Does the 'good' bacteria actually live on the rocks and other objects or does it float around? Also the filter is not exactly a huge source of 'good' bacteria, correct in that not a lot comes out of it, rather the bacteria lives in it?

If that's so, there's no problem running the UV in line with the filter's line that goes back into the aquarium, correct?
 
Check the flow rate recommendations for your UV. Unless I missed something in your description (which I probably did), I'm thinking that the main return flow rate might be a bit too fast to kill stuff it's supposed to.
 
As far as everything I've ever read... the bacteria lives on the surfaces of objects in the tank.... no problems with killing off free floating bacteria....
 
Nothing good floats around. Including fish as they create waste and change the waters chemical stability. But of course we dont want to fry them. :) Just make sure your pump will be able to cycle the entire tank twice per day and no greater than 180gph through the filter. 180gph x 24h = 4,230gallons, technically a 2000gallon tank. 180gph x 8h = 1440/2 = 720gallon tank. Technically speaking you could even slow the flow of water down even more than that to maximize the effectiveness of your sterilizer (much like I have). I have an 8w that is designed to filter 1000gallon pond in a 24 hour period (designed to make green water clear). Mine is designed for 83gph for 24 hours super sterilizing things in a 1000 gallon. Obviously I can run it for half as long, and at half the water flow - but due to recommended minimum specs, you shouldn't go under 60gph to maintain bulb life (these things run hot but do not significantly affect water temp).

*note - gph numbers are reflecting head pressure of ~4' of tubing.
 
Okay well my filter is 1500L/hr which is around 396 US gallons/hr.. seems a little fast, right? What do I do in this situation?

In actuality I don't think it runs at 1500L/hr as I have two 1500L/hr power heads that have a faster water output than this filter.

That being said, what can I do? Do I have to get a higher spec UV unit?
 
Your pump should have come with an adapter to adjust the flow (plugs onto the output and limits flow via a knob). It may also have an adjustable arm on the bottom. All in all, I might just suggest a smaller pump (a 210/310 or < Rio 800), as too much flow essentially negates having the sterilizer at all, and limiting a larger pump that could be put to better use (feeding a carbon filter or anything else).

..a bigger UV sterilizer wouldn't make a difference unless you had one that held a full-size flourescent tube-uv bulb (not realistic in otherwords). As I said before, my 8w is overkill for my 75gallon tank... but then again, there's no such thing as being too filtered.
 
there are adjustable valves which allow me to restrict water flow equally on the in and out lines. that being said, i am not going to buy a new filter just for a UV unit.
 
You can add a bypass line to the filter return line. That will allow you to adjust the flow to the UV unit without affecting the flow through your filter. Check out this article for more info on flow rates, wattage, and recommended zap dosage for UV sterilizers. One point I should make is that, for example, having 100gph flow through a UV unit with a 100 gal tank does not mean the tank cycles once per hour. At first glance, you'd think it would but you have to remember that the sterilized water is mixing with the unsterilized water as it's pumped back to the tank. Anyway, here's the article which explains all this in more detail: http://www.aquariumadvice.com/showquestion.php?faq=2&fldAuto=39
 
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