To UV or not to UV, that is the question

[mgoesma]

Ozone is a gas (which is a bond of 3 oxygen molecules, the same gas that makes up the ozone layer). The third oxygen molecule is volatile and quickly breaks off and attaches to something else, most often organic waste molecules in water. This causes them to oxidize, thus breaking down further. Yellowing compounds or organic waste in water is easier for a protein skimmer to remove once it has been oxidized. Ozone's oxidizing effect raises water's ORP (oxygenation reduction potential). Some people believe a higher ORP value means purer water, but there is argument to whether or not that is valid. It's pretty commonly accepted that water with an ORP value below 200 mv has a high organic waste load. Natural seawater surrounding coral reefs has an ORP of around 450 mv. The oxidizing effect of ozone is very effective at breaking down yellowing compounds in water, making it highly effective at ultra-clarifying marine water. Ozone treated water often has a hallmark ice-blue appearance.

The oxidizing effect of ozone also kills parasites, but oxidizing them. Yet, the problem with UV sterilization remains with ozone. Ozone is used in aquaria either in a reactor or injected into the skimmer. Parasites within water that enters the reactor or skimmer chamber is stripped of parasites, depending on how much ozone is injected. Yet, there are still parasites on fish tissue, rocks, the sandbed, etc - which survive in the presence of ozone injection. Ozone's most effective at raising ORP, clarifying water and aiding the skimmer in removing organic waste by oxidizing it beforehand.

The health risks of using ozone are two-fold. One, any stray ozone entering marine water can be detrimental to all marine life. Any effluent leaving an ozone reactor or skimmer chamber must be filtered over activated carbon to remove residual ozone. Furthermore, ozone injection must be done on a controlled basis and monitored by an ORP controller. Too much ozone will violently raise ORP and can oxidize fish/coral/invert tissues. An ORP controller measures ORP and shuts the ozone generator off once ORP gets to a preset mv reading. Also, ozone is not healthy for human beings to breathe, therefore air leaving a skimmer or ozone reactor must also be filtered with activated carbon. This can easily be done by covering a skimmer cup with a carbon bag. Most ozone reactors are air-sealed and effluent travels into a carbon reactor before returning to the tank.

All this said, there was a study done on a group of ich infected fish in a bare-bottom tank with no decor. The only treatment for the parasite was ozone injection. It was found after 30 days that the parasite was eradicated. Researchers believe the bare bottom, decor free environment contributed greatly since the parasites had no medium within the tank to adhere to, other than fish flesh. They also believe an immune response within the fish contributed to the experiment's result as well. In a reef environment, it's highly unlikely ozone would be nearly as effective.

I personally believe my tank is clearer when ozone is used to clarify water instead of carbon alone. That isn't saying this is scientific fact, but just noting my own personal observation. I also believe my tank is healthier when the ORP is around 350-400 mv, which is achievable in my system only through the use of ozone injection. Again, just my observation, not scientific fact. Ozone nor UV sterilization is required for a healthy/beautiful marine aquarium. Proper QT and stocking procedures are far more effective at preventing parasite outbreaks then either ozone or UV.

Do you know who preformed this study?
I am not a Ozone expert but I have read quight a few papers about it. from my understanding the Hobbiest level ozone reacters will not kill parasite/bacteria. It is simply not strong enough. This is similar to a cheap UV sterilizer. Also if you use an industrial Ozone system, like the water company uses. yes it will be remarkably good at killing bacteria and parasite the only issue is if it is not used correctly and filtered out correctly it could cause Major health issues for you and your tank. (if it smells like a lightning storm you have Ozone in the air and should take action) Also I think it is important to note that Ozone is extremely corrosive. Oxidize is another word for corrode it how the thing works. Also I think it is important to note that ozone does not remove anything. It just breaks it down and then you have to filter the ozone with charcoal.
This is why I decided to just skip all that and use charcoal to filter the water. I would agree that ozone probably does a better job but hey, I'm a newbie and I think the added expense and danger out way the benefits.

 

[jeremy.gosnell]

The study is mentioned in this paper from the University of Florida and this study for the seafood industry. Hobbyist level generators vary in their size and effectiveness, but are powerful enough to kill parasites and bacteria, depending on how they are used and the tank's size and nutrient load. It would be possible to totally sterilize a marine aquarium of moderate size (100+ gallons) with several on-the-market hobbyist generators. For example, marine water of anything 600 mv and beyond would kill everything in a reef tank. That could be attainable with a powerful hobby grade ozone generator, cranked up to the max. The generator I run which is an OzoTech Poseidon (very common generator) keeps my tank at around 350-400 mv on the lowest setting, 1 out of 10 settings (10 being the max). The tank is just shy of 250 gallons. It's quite likely that parasites and bacteria within the ozone contact chamber (or skimmer chamber) will be killed, as this is an area of active ozone introduction.

Ozone breaks down plastics/silicone that aren't ozone rated. They are highly effective at it, drying the plastic out and causing large cracks that eventually cause tubing and other materials to disintegrate. This is easily overcome by using ozone rated plastics and selecting ozone rated skimmers. As for corrosion, that is possible if the air entering an ozone generator contains moisture. Aquarists use a desiccant filled reactor to dry air before it passes through an ozone generator, which removes all moisture.

You're right that ozone does not remove anything, but it's oxidizing action does break down complex organics. That action alone can render them less detrimental to water quality and also makes them easier for other filtration methods to remove. It's also worth noting that long-term ozone is actually cheaper than carbon to use. The up-front costs associated with ozone are higher than using a carbon reactor, but long-term there is no filter media to change and ozone generators use a very, very small amount of electricity.

Most hobby level generators use an electrical coil system to generate ozone. When air is passed through the generator, electrical discharge breaks up the oxygen molecules. Some of these molecules re-assemble as O2, while others re-assemble as 03, thus creating ozone gas.

 

[jeremy.gosnell]

Do you know who preformed this study?
I am not a Ozone expert but I have read quight a few papers about it. from my understanding the Hobbiest level ozone reacters will not kill parasite/bacteria. It is simply not strong enough. This is similar to a cheap UV sterilizer. Also if you use an industrial Ozone system, like the water company uses. yes it will be remarkably good at killing bacteria and parasite the only issue is if it is not used correctly and filtered out correctly it could cause Major health issues for you and your tank. (if it smells like a lightning storm you have Ozone in the air and should take action) Also I think it is important to note that Ozone is extremely corrosive. Oxidize is another word for corrode it how the thing works. Also I think it is important to note that ozone does not remove anything. It just breaks it down and then you have to filter the ozone with charcoal.
This is why I decided to just skip all that and use charcoal to filter the water. I would agree that ozone probably does a better job but hey, I'm a newbie and I think the added expense and danger out way the benefits.

If you're new to reef keeping, that last thing I would recommend is that you install an ozone generator on your tank. New aquarists have enough to adjust too, without the added concern of installing and managing ozone introduction. However, for more advanced aquarists who are looking for a way to reduce parasite/bacterial load in aquarium water, while also harnessing some other benefits, ozone might be worth a look. However, it's primary use is to clarify marine water.

 

[jeremy.gosnell]

This link also has some interesting information about marine fish parasites.

 

[Valkyrie]

Ozone does not sound like anything I would be remotely interested in

 

[mgoesma]

If you're new to reef keeping, that last thing I would recommend is that you install an ozone generator on your tank. New aquarists have enough to adjust too, without the added concern of installing and managing ozone introduction. However, for more advanced aquarists who are looking for a way to reduce parasite/bacterial load in aquarium water, while also harnessing some other benefits, ozone might be worth a look. However, it's primary use is to clarify marine water.

I agree with this.
Question. Don't you still have to buy Charcoal and replace it in the Ozone filters? Wouldn't that cost be a wash?

 

[jeremy.gosnell]

The amount of activated carbon needed to filter effluent from an ozone reactor or skimmer output pales in comparison to the amount of carbon needed to filter an entire tank. About 2 oz of activated carbon is plenty to filter effluent leaving an ozone reactor. Also, I use Filtrete carbon pads on my skimmer cup to filter air. Since I already buy the filtrete material for my home's air purifiers, it works well.

 

[armspar]

A UV sterilizer is great to have no question. It can kill some parasites but most of the extoparasites reside in the sand and the rock, so you won't make much impact with a UV sterilizer. It can help by chance that the parasites happen to go through it but not a great use for a sterilizer.

 

[RMS18]

Does it help kill parasites? I don't think so... does it make the water clear as crystal yes. And for that reason I have one.

 

[bubbaque]

Is it possible to oversize a uv sterilizer? A local fish store said they have a 55w in stock but worry that is too big for my 80gl total water tank.

 

[brandon429]

not possible
undersizing or correctly sizing is the crime

I ran a ten thou gallon pond sterilizer on a 75 for 11 yrs and cheat burned every invader. any bac killed are incidental any pods can be just retail fed replaced

 

[bubbaque]

How bad does it heat the water up?

 

[brandon429]

nice call, mine had no impact but then again I ran evap cooling in that old rent house and it was hot all the time anyway. that heat factor is a fair consideration for hardware effects, biologically its ok to do.

 

[ARGYGANG]

UV isn't a horrible option if budget is no object, but it's expensive to do right for your purposes. I think it's a better fit for commercial scenarios where new livestock will always be coming into the system. You system still be mostly stable over time, so the benefits should be less.

Beyond this, I'd only add that all methods listed so far are not foolproof and there doesn't seem to be any advantage to thinking otherwise.

The alternative – stocking slowly so the fish you add have time to get healthy – might be the most successful strategy. But not due to any genius on my part – just because it gives the fish time for their immune system to recover from all the trauma and stress induced by being repeatedly handling and constant handling.

There's no magic number for "slow", but I usually recommend that people wait one or more months between livestock additions.

Adding too many fish too quickly allows none of them to heal and may even compound any existing issues (even ones you haven't had time to catch yet) so you end up with a tank of weak fish along with whatever disease they could bump into on the way to your tank. Definitely not the goal.

Also important is that your skills never had a chance to develop either if you stock a tank up in the firs month or two.

So after all (even with dip, QT, TTM, et al) what you get it a tank of weak fish being kept alive by a newbie. It doesn't take much to upset that apple cart.

I think this applies most strongly to fish, but also to pretty much any organism you'd think to put in your tank.

@Paul B has said quite a bit on this front.....highly recommend his book.

It’s been 6 years but I can vouche for this, my entire tank was wiped because I stocked to quickly and didn’t let the fish distress and heal back up from different tank swaps etc.