I´m also "sorry" to say - since I start my new aquaria (2 years ago) and run an oxidator 24/7 - I´m in the same situation as najer. I do not either QT my fish but before I introduce newcomers - I let them be in my refugium for a week or two. This does not mean that this is because of using an oxidator because the disease situation seems to be different in EU compared with the situation in US.
However - I normally do not use things because of fancy words and so on - I use them because I know that they work or that I understand their function. Peroxide is an oxidiser - very aggressive - and form oxygen radicals of different types. Oxygen radicals is one of the most common natural "cell destroyer" that exist - many organisms use it as a defending tool (our macrophytes as an example) and therefore - among many multicellular and more advanced organism there exist a defence against active oxygen radicals - antioxidants. It means that more advanced organisms normally have develop a defense mechanism against free oxygen radicals - our sun burn as an example (read production of melanin). Photosynthetic corals - with a producer of free radicals inside their tissue - can be assumed to contain a lot of natural antioxidants too. Fish do contain a lot of this - crustacean the same.
It have been shown that bacteria, algae and some parasites will be oxidized by this active oxygen radical because of lack or not production strong enough of antioxidants. Some marine phytoplankton has high content of antioxidants but it seems like they also are sensitive to free oxygen radicals.
When I run my oxidator in the manor I normally do - 6 % H2O2 and 2 catalyst - I have not seen any negative effects to attaching microalgae (important for me to have a production of this because it is a food source for my large clean up crew) or anything else that is important for me. The pro I got (that I can show) is rather clear water (most of the yellowing substances will be oxidised and I have a huge production of them because of the construction of my refuge and I do not do any WC). The way this low concentration of peroxide theoretical can act on parasites and aggressive bacteria is to minimize the amount of them and let the natural immune system of the fishes develop.
I´m totally adware of the fact that if I get in an active infected fish of whatever - the amount of dangerous microorganisms can be to many and break through the normal immune system and that i need to rise the dosing of peroxide.
The linked thread from atoll shows that it is possible at least with infections of Cryptocaryon irritans. When I introduce newcomers I normally rise my H2O2 concentration to 9- 12 % - still 2 catalyst (I have more in reserv if I need).
Is it reef safe? Normally - yes I think so. I have one caveat - in systems (or time) with high natural oxygen production from photosynthesis and especially low flow systems - there can be a problem with to high concentrations of active oxygen radicals from other sources than the corals own production of these active radicals. The natural defence system may be too weak. My solution to this should be to lower the light intensity during the active treatment period with higher concentrations of peroxide in the water (lower the light intensity - lower the photosynthesis - lower the natural production of radical oxygen species). Is it necessary to lower the intensity of the light - I do not know but this can be one reason why the reviews of Polyp Labs Medic differ so much about reef safe.
How does this "magic" doser work? IMO - it is one of the most ingenious solution I have seen.
A pic of the parts of my oxydator (there is other models but the working mechanism is the same. In the acrylic bottle you pull your wanted H2O2 solution and the number of catalyst you need (a catalyst is a smal part of the same clay as the cover and the top consist of). In the orange cap - there is a little hole. You need to use distilled or good RO water in order to mix your solution
You turn the acrylic bottle upside down and put it in the in the ceramic outer bottle and put the round top over the acrylic bottle.
After this - you put the oxydator there you want it - I have put it in my sump just there the overflow from the skimmer apartment come out to the return apartment. Water level 10 cm above the top of the oxydator.
What´s happen now? The catalyst start to divide the H2O2 into H2O and free O atoms. The free O atoms will directly find another free O atoms and form Oxygen gas. The rate of Oxygen production is determined by number of catalyst and H2O2 concentration. The produced Oxygen gas will rise to the top of the upside down acrylic bottle and form a pressure that force uncatalyzed H2O2 out through the tiny hole in the orange cap into the space between the ceramic outer bottle and the acrylic bottle. The ceramic will catalyze most of the H2O2 and the free O atoms will form oxygen gas or oxidize organic matter - depending on what it hits first. Depending on concentration and number of catalysts some H2O2 will not be catalyzed and coming out in the water column and slowly form active oxygen radicals as free O atoms and others which will oxidize organic matter like yellowing substances and organisms with no or weak defence system against free oxygen radicals.
The concentration of H2O2 and number of catalyst is the toll you use in order to get the effect you want and it will give this continuously 24/7. There is a risk of overdosing - there is not easy to determine the concentration for the effect you want. You have as usual to observe you animals and see how they react.
When I write this post I realized the danger with combination of H2O2 dosing and high photosynthesis and I think that if you want to treat a existing reef - against an outbreak of what ever - with higher levels of H2O2 - run your light rather low during the treatment period.
Sincerely Lasse
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