Backyard Aquaponics
A place to discuss aquaponics

That is good to hear that you are back in the game.

Cheers

Glad to hear that the lamp made a difference.

I only ran mine every few weeks when water starts turning green.

Gabe

Gabe,
are you suggesting that there may be a negative effect if the UV light stays on permanently? Does it destroy usefull bacteria for example?
This weekend I am going to install a bypass for the filter to allow me to backflush and clean it online. This could be my opportunity to switch off the light which I will have to do anyway...
over to you Gabe...
regards,
Marticulus

Yes, constant use of UV will be detrimental to "useful" bacteria... use it when required...

Thanks guys! This forum is brilliant - I have learnt so much...
Next is trip to Ferguson Valley to buy silver perch...
Cant wait till weekend...
Marticulus

Rupe, I've read UV clarifiers kill off bacteria in the water column, but most of the nitrifying bacteria reside on the solid surfaces?

edit: even so, I would still only turn on the UV filter when required.

I'd be more concerned about this:

"the continuous use of UV will cause certain mineral elements [Iron and Manganese] to drop out of solution very quickly"

http://www.diyaquaponics.com/forum/view ... =90&t=1553

..it's hard to find any good studies on either side of the debate on the effects of UV clarifiers to nitrifying bacteria in ponds. Best I've found so far is the anedotes from the planted tank folks (who really love their plants )

Of course there's this guy who goes into a fair bit of detail, but who can trust a guy toting the pro's of UV whilst selling the units from the same website, right?

"..most organic compounds are either destroyed or weakened by UVC Sterilization (at optimum levels). As I have noted elsewhere this includes nitrifying bacteria, HOWEVER this bacteria is rarely in the water column and should NOT be in the water column, so this is not a problem under most instances other than adding cycling aids (during such time UVC Sterilization should be discontinued for 24 hours as noted earlier)."
http://www.americanaquariumproducts.com ... ation.html

I wanna see some studies

I did trial constantly running a UV clarifier for six months on one of my 2000 litre aquaponic systems last year, I couldn't notice any detrimental effects (kept feeding rates the same, didn't detect any ammonia, plants seemed fine), but I would really like to see a better side by side aquaponic comparison done. Same plants, same fish load, same feed rates etc. Need some hard data

I'm sure that freoboy ran a UV steriliser on his system constantly

Think I found his thread with the UV clarifier:

viewtopic.php?f=18&t=7916

Would be good to hear his experiences with running it

So according to both those links Jono... UV acts as a steriliser... killing pythium, most suspended bacteria and many viruses in the water column,... and parasites such as Ich or Cryptocaryon ...while not affecting bacterial colonies in filter media and substrate...

Find it difficult to believe that a UV lamp could be so discriminating between strains of bacteria...

It might not directly affect the bacterial colonies residing within water bound to media and/or substrates... but I'm sure a lot of nitrifying bacteria actually are in the water column at some point of time...

From memory... I think Rakocy said 90% of the nitrifying bacteria were resident in the water in the UVI system.... but I'd have to check that...

He might have said... that 90% resided on the DWC trough surfaces... (sounds more likely)...

There will be nitrifying bacteria everywhere in an AP system. If you have very robust filtration, then killing off a portion of bacteria that happen to be floating around in the water column at the time with a UV light is probably not measurably detrimental to the system though.

Probably the main reason not to leave the UV light on all the time is that if you don't HAVE to have it running full time to take care of your problem, then you can save a bit on electricity and lamp life.

If your system is a raft system without ample additional filtration. (like a Friendlies "low density" system perhaps pushing the limits of the filtration) then it is likely that running a UV sterilizer might actually produce a measurable fluctuation in your filtration capacity since those systems can sometimes be so limited on their filtration capacity that simply harvesting a raft of plants all at once will reduce the surface area for bacteria in the system by removing so many plant roots all at once that it could cause ammonia spikes.

Yes Rakocy did do some research into nitrifying bacteria in the water column. I don't remember if he even said a % but they did do something where they took water and placed it into a separate container and then added some ammonia and then measured the next day and the ammonia was converted to nitrate which confirms that there is at least SOME nitrifying bacteria in the water. Now many could argue that the bacteria are actually colonizing the surfaces of particles in the water but since those particles are floating in the column it means about the same thing as the bacteria simply living in the water when it comes to the effects that a UV light would have on those bacteria as they float on a particle through the sterilizer.

On that note about using a UV sterilizer to get rid of algae, the UV will likely do a great job clearing free floating algae that is causing green water but if you are worried about string algae or surface algae, I don't think UV sterilizers or clarifiers are going to get rid of that problem for you since it will only kill what is pumped through it.

From my understanding, that's not what they are saying. More that the majority of nitrifying bacteria cling and live on the solid surfaces (unaffected by the UV light), with a minority free floating in the water column which of course would be affected by the UV, but not enough to adversely affect the total bio-filtration capacity, they claim.



Got a link to the study? Closest I can find is this one:

"Feed was restricted slightly during the first 4-6 weeks of the trials until populations of nitrifying bacteria in the water column were adequate to maintain low levels of ammonia and nitrite."
http://ag.arizona.edu/azaqua/ista/ISTA9 ... akocy2.doc

..and this:

"...after an initial acclimation period of one month, it was not necessary to monitor ammonia or nitrite values in the commercial-scale system provided that the film on nitrifying bacteria on the underside of the rafts remained intact"
http://ag.arizona.edu/azaqua/ista/ISTA9 ... akocy1.doc

If these are the studies you refer to, they're not really definitive either way on the amount of Nitrifying bacteria living in the water column compared to on the solid surfaces?

I'm not convinced yet either way..

For example, during cycling? I think that's why the bloke in that link (http://www.americanaquariumproducts.com ... ation.html) was recommending UVC sterilization should be discontinued whilst adding "cycling aids" (Bottled Nitryifying baceria?) - presumably to allow the nitrifying bacteria settle and attach on the hard surfaces

Again, too much guesswork here.. would love to see a study done

Just found this topic..

One thing come's to Mind What are the system's reading..

pH , ammonia and such..

I had a similar issue with my very first pond that went Pee Green..
- IT was fine for the first 9month's of it's Life then it went Green and the water clarity was up the creek..

My fix was to install a Sand filter in system..[using Shell Grit] instead of the sand..

the filter is coming up on 4year's old and It has been topped off numerous time's..[more shell Grit]..

that filter is about to be retired as it is over full of crud....[ I have not been able to do a proper clean of the media in 6month's]
The shell grit's going to be dumped into the new system....[ growbed ]

I have not had bloom in that pond since..

and yes it does sound like the sludge issue is the stuff from the pond..

Juergen

Reading through my notes quickly last night... I think that's indeed the case....

It's not so much that UV kills the bacteria... but breaks down the suspended organics surface area that they would populate...

Hence it doesn't affect the bio-filter to a large extent...