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What do you think of the use of ozone in a marine aquarium?


I hear lots of different views and advice on debating whether or not to use ozone in a marine aquarium with and without a protein skimmer, i personally use it in my marine tank for the visual sharpness of the water it achieves, and secondly because i love the smelling it! (okay, the second one was a joke!) :lol:

I have owned and used and repaired a few different brands of ozonizer, and i think they are great pieces of kit for water management, now i want to know what you guys and gals think of them?


i have never used one but i know places like seaworld use them to sterilize their water ,obviously on a much bigger scale and it keeps the whales and dolphins healthy so cant be to bad


One of two questions need to be answered here I think.

1. Are you running ozone just to polish the water

2. Are you running ozone to eliminate an outbreak of whitespot or other parasitic problem.

When you have answered the question above then I think you can start to look at the various options.

I would agree that running an ozone unit for say a couple of hours at night to improve water quality is fine to do controller free. As long as the dose is low (based on tank size and ozonizer capacity) and it is only for a couple of hours then the need for a controller has to be questioned. In this case I would doubt the Mv level in the system would reach a level that could become lethel to the aquarium.
Also on the above method there is very little risk to the people in the home as the ozone is on during the night when most people are in bed. As long as the room is well ventalated and the tank is not next to your bed this method should be perfectly safe.

On the note of running ozone to remove WS or other parasitic problems then the situation is slightly different. The dose of ozone (Mv) level needs to be increased to 350-375Mv for it to impact on the said problem. At these sorts of levels it is a fine line IMO between being used effectivly and becoming dangerous. In this instance I would say a controller is a must have.

Let me give you an example. I ran the ozone via the controller and probe to help with a slight whitespot issue. The controller was set to 350Mv and all looked well. However what I did not know is I had a faulty probe (very rare). The level set at 350Mv was infact a dose of around 430Mv. Result was almost total wipe out of all livestock. The difference between 350Mv and 430Mv is not a big one on paper but in real terms is the diffrence between ozone being effective or ozone becoming a disaster.

On the above expirence that I had I learned the following.

1.Treat ozone dosing with respect and slight caution.
2.Calibrate and check the probe weekley
3.Run Carbon both after the ozone has mixed in the skimmer and on any air escaping from the skimmer
4.If done correctly it can be both safe and very effective.

The level of 350Mv is posted time after time as being an effective level and a 'safe dose'. However if you decided to achieve this level without a controller then how do you know you have reach the 350Mv level? In short you dont and if you over shoot this then you could be asking for trouble.


That was a very interesting reply, cdurkin100,

yes i use ozone to both polish the water in which i use the dosage of 10mg/100 liters so i'm currently running 50mg/hr in my 550 liter fish only system, (well invert, as it has a lot of live rock), and without a redox controller i would say its at a very safe level, ( 3 years plus) and i could even use more, and have used more, theres no smell of ozone in the system, and livestock are healthy :)

I also have used it in a protein skimmer and even with impressive results, i rather run it seperately, as my v2skim 800 has never so much as collected anything when ozone was running on it, so now i have this ozonizer hooked up to a hi blow 20, feeding ozone into a separate compartment in the sump and being diffused through a couple of 12 inch airstones.
Now i have done that, the protein skimmer does collect waste, but never enough as to even half fill the cup, (my tank is lightly stocked).

I've never believed in using high amounts of ozone to kill of parasitic infection or whitespot, i'm a preventative kind of guy and if there was any need, i would take out my fish and treat them seperately, in vats with filtration and other requirements set up. Though i DO believe that its good to use to keep possible infections and out breaks of whitespot due to stress to a minimum in ANY tank. Besides, the time and level needed to make a real difference may actually harm livestock unintentionally.

I've never actually used an ozonizer personally when it was set on a timer, i've always used them on continually, even in my late reef tank, i had to break down due to lack of time and budget. I always though that theres was no point in having it on half the time or less, just like people who say they run there u.v sterilizers for 6 or 12 hours per day, and people who do the same to their protein skimmers.

I agree fully on your veiw on its effects on humans, yes high amounts can cause health problems, but too much of everything could harm or kill us, but when i had my reef tank and ultra small fish only system running side by side in my bedroom, i used ozone on both of them and during that 3 years, no dangers of health emerged to me whatsoever!


I use a 50mg/h unit for my 550l reef and I use it through an mV controller.

I have the mV controller set to 350mV.

I have to say that the ozone is very rarely on and the water is crystal clear.

My probe is checked regularly.

So the moral is that even with a low dose the mV controller seems the thing to do in my opinion.