Greetings from Melbourne, Australia

[foodchain]

I think we will have to disagree. Years of PROVEN application amongst public aquariums, aquaculture facitlities, universtities, fish farms, etc and my own applications in marine, marine aquaculture, and freshwater are more adequate proof for me that these statements above are inaccurate.
IF what you are saying above is true in application and not just theory, then for at least the last 20 years we have all been doing it wrong. The probability of this is next to none. However as the hobby grows, we uncover new things and new ways of doing it. So there's a possibility, but very slight.
I will concede on this though, and tell you to do as you wish with your own systems. Mine, as I push production to the very limits probably further than I should. And I run population concentrations very high by comparison to most people, I HAVE to have the sterilizers, or run the risks of epidemics I can't recover from. The risk of losing it all far outweighs the minor electrical consumption or the bulbs as they have to be changed.
For me, it's not a hadfull of fish, or even a couple five gallon buckets worth...
I can't risk the shear volume of fish, and potentialy having to break a whole system down on a hunch that goes contrary to world wide application. I have yet to see any data that supports your statements that UV sterilizer will kill off all the bacteria.
But I do acknowledge that everyone's systems are different, and while requirements may be similar. Applications are different.
The absolute best thing I can say is: Do as you wish with your own systems. Do what works for you. For me, I guess I will be a little less effecient on the electrical, but my fish, my inverts, etc will all be healthier.
Best of luck which ever way you go.

[bsfman]

I don't have near the knowledge or experience of some folks here on this forum, but that being said, I've viewed aquaponics since day one as a pyramid. At the base of the pyramid are the nitrosomonas, nitrobacter, heterotrophic and autotrophic bacteria that sustain the system. Fish are in the middle of the pyramid and plants are at the top. My view has been that I have to maintain a system friendly to those various bacteria in order to form a base for the rest of the pyramid. It seems to me that anything that is counterproductive to maintaining that healthy bacteria population is counterproductive to the entire aquaponics ecosystem. Bascially, aquaponics keepers are successful bacteria farmers.

That being said, I've always been under the assumption that UV pond lights are primarily used for algae control. But in aquaponics, I view algae as a good thing - an indication the bacteria are busy converting fish waste from chemicals harmful to my fish, to chemicals beneficial to my plants (and a certain amout of algae growth).

I suspect those public aquariums using UV sterilizers are doing so not so much for the benefit of the fish as they are for the benefit of paying customers who wish to view the fish through crystal clear waters.

But I could be wrong. (I've often been before)

[foodchain]

UV is used for algae control in ponds/stock tanks. BUT
They are used in aquaculture and many marine systems for disease and bacteria management.
In the end, they do both though. They are meant to sterilize the water. By doing this, they actually do a lot of things. Whether they are for you or not, is up to you. Algae by itself is a result of excess nutrients in a system, it's not good or bad, it's an indicator of what's going on your system...
Systems that do run them have significantly reduced the risk and out breaks of a great many parasites, and other ailments. It's just a tool people...it's the right tool for the right job. For me, it's preventative medicine, and has proven to be just that for a great many for some time. Some folks do just fine without it.
I have done both, and after matching the right UV to my setup, and gaining some understanding in them, I won't go without them. When I just had feeder goldfish and they died it wasnt the end of the world as the replacement cost was minimal. As my collection, and invested expense has increased though, the risk of such losses is no longer a financial option to replace or excessively risk when so easily preventable.
Some folks won't build big enough GB to support their bioload, so they have to do partial water changes too or install additional filters. Just because they do it that way, and it doesn't make one right or wrong. It's just the way they do it.
Is there a better way? Depends on what their budget/space, spouse will allow. I can't tell them they are wrong, who am I to do that? What I can say, is for me...there's a better way to do it. Or I can say, have you thought of?

[keith_r]

right.. you're talking aquaculture..
aquaponics is a different animal so to speak.. most backyarders do not use UV, nor do they need to... most "fish problems" are the result of power outages causing depletion of do, drastic temp/ph swings, or improper monitoring of levels of am/ni/na and not reacting to problems..
UV doesn't have any impact on any of these, and may in fact give the backyarder a false sense of security..
the bacteria are going to be in a system no matter what you do, but by avoiding causing stress to the fish is the best way to keep your system healthy..

[foodchain]

But fish disease, parasites, and bacteria aren't.
My "aquaculture" system is my backyard system. Simply instead of running one fish, or one species, I opted to maximise the available space and run it as a polyculture. Keith you are doing something along the same lines already with the crays and YP. Just not as extreme as my setup, but the idea starts to grow, and before long you have several species all in the same water.

[foodchain]

Its the same concepts is all I am saying. The parasites, algae, etc don't care if it's just aquaculure, AP, or out in the lake. They react/behave the exact same way in regards to their cycles. It's the cycles they go through that makes them susceptable to the UV.
No, you don't have to have UV. No I don't HAVE to have it. But again the cost of replacement of my aquatics, vs the cost of the UV in MY application make it a no brainer. In your's Keith it doesn't, not yet. IF you continue to add different species it may not be a bad idea.
They do more benefit than harm.

[foodchain]

You are absolutely right, reduction of stress, especially as a preventative is worth an arm and a leg.
Please keep in mind though, just like any agriculture the denser you run your livestock the faster diseases spread. UV is a tool for me to contain the risk. Nothing more.
An ounce of prevention, whether by stress reduction, proper water parameters, temps, etc will always be better then a lb of cure. This really is true.