Re: the use of UV filters for algae control

On Wednesday, 31 May 1995, Stephen Pushak wrote:

> Jon brings up an interesting topic; the use of ultra-violet sterilizers in
> filtration to kill algae (and other bacterial organisms). Does this work
> well? Will it work on brush or black algaes? How expensive is this option?
> If I remember, this works very well on ick parasites.

I have a 15W Aquanetics unit on my 135g fish/plant tank, which I
operate continuously at a flow rate of about 120g/h.  While it keeps
the water crystal clear (no suspended bacteria or algae), I still have
quite a healthy growth of algae on the glass, gravel, and several
plant species despite a good number of algae eaters (3 Farlowella
gracilis, 1 F. acus, 4 ottos, 1 generic pleco, and one Peckoltia
vittata).  Remember that a UV filter only kills organisms that get
sucked into the filter, and in a heavily planted tank there are plenty
of places for algae and parasites to reproduce.

Recently I started measuring iron in the tank with a Sera test kit.  There
was no measurable iron despite weekly fertilization with Sera aquatic
plant fertilizer.  As an experiment I started adding 1/4tsp/day 7% iron
chelate but was unable to get the iron concentration up to the 0.25mg/l
mark (the first level on the color chart).  I can't believe that the plants
are consuming iron this fast, so either the carbon is binding it up (I'll
test this possibility soon) or the UV is oxidizing Fe+2 to Fe+3.  If
removing the carbon doesn't help I'll turn off the UV for a week and see
what happens.  A better test kit might be in order too, but adding a speck
of chelate to the water sample produces a dramatic color change, so
my test kit isn't totally out to lunch.
Kevin Conlin   kcconlin at cae_ca   "We're Canadians.  We HAVE to be polite"