Re: Aquatic Plants Digest V1 #98 Re: the use of UV filters for algae control

On Wed May 31, Kevin Conlin wrote:
>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.

1/4 tsp. per day isn't all that much if you have good plant growth.
Still after two or three days it should register at the first level.
EDTA chelated iron is subject to decay of up to 80% in the aquarium
over a two week period. Water circulation and especially light hasten
this effect. God knows what UV radiation would do. Three years ago
I wrote an article in The Aquatic Gardener concerning the various
chelated irons and micronutrients. I posed the question of the likely-
hood of activated carbon removing chelated metals from the water since
EDTA and DPTA were organic molecules. Someone replied that it could
be easily tested if one had carbon, which I do not.

Why do you bother with UV sterilization and carbon anyway? Those
cyclops have to have something to feed on.