Ultramarine Magazine Issue 64 JuneJuly 2017

Myth-busting:

Higher ORP = healthier tank

Redox values can give a simplistic indication of the

‘cleanliness’ of water, but it’s important not to strive

for artificially elevated values. Ozone dosing can raise

redox, but don’t push values too far – over +400mV,

you’ll run the risk of a wipeout from the direct effects

of residual ozone or from ozone producing toxic by-

products. Bromine, for example, reacts with ozone to

produce hypobromous acid (HOBr) which is extremely

dangerous for fish. Many public aquariums use low-

bromine salt mixes to guard against these effects.

Some systems run just fine with ozone at +250mV,

some at +350mV, so don’t become fixated on bumping

up redox just because you can. If you’re achieving clear

water and the system is running well, that’s all that

matters – but measuring redox gives an indication of

when you’re nudging the ‘danger zone’ of +400mV to

+450mV.

Myth-busting:

Ozone sterilises aquarium water

In normal usage, ozone will have some effect on patho-

gens; for example, it may reduce bacterial and parasite

loading. However, studies have shown that very high

redox levels (in the +800-900mV range) are needed to

really disinfect water, which we wouldn’t come any-

where close to achieving in practice. As with UV, how-

ever, those aquarists employing probiotic techniques

which rely on free-living heterotrophic populations

should be mindful that ozone could negatively impact

the bacteria which are being encouraged. This may be

an issue if higher doses are used, but lower doses may

have minimal impact.

Free ozone is very dangerous in the aquarium, so the effluent of

the skimmer should be passed over activated carbon. This helps to

mop up any residual ozone. Ozone can also be gassed-off from the

skimmer’s collection cup into the room; to deal with this, place a mesh

bag of carbon over the cup’s air holes.

through the use of a redox (ORP

• oxidation-reduction poten-
  tial) controller and probe. The
  controller is programmed to
  switch on the ozoniser when a
  set redox point is reached, and
  switch it off when a maximum
  value is achieved. Remember to
  check or calibrate redox probes
  regularly, as fouling can cause

readings to drift.

Alternatively, many aquarists

select an undersized unit and

dose a very small amount of

ozone constantly, or have the

ozoniser running for perhaps

only a couple of hours a day.

Whatever approach you adopt,

start slowly, and build up the

dose over time.

Check or calibrate probes regularly, as readings can drift.

This small ozoniser allows for the dosage to be dialled up or down, and for the

timing of dosing to be programmed, making it quite flexible.

48 http://www.ultramarinemagazine.co.uk