Modifications of ETSS-type skimmer ?

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I have a 150 gallon reef tank which came with a custom-made ETSS-type
skimmer which sits in the sump. Although I have read that in general
this is a good bang-for-the-buck design, I have been thinking about
trying to improve the skimming in my tank because the tank has had
persistent levels of phosphate in the .1 range despite moderation in
feeding. I cannot simply buy a better skimmer with a taller reaction
tube since my cabinet height is low. I have been considering making a
modification in my skimmer as follows. In a ETSS skimmer, water is
pumped at high velocity at the top of a tube which contains bioballs.
The water/air bubble mix travels down the tube, and then is allowed to
flow up a reaction tube where froth can overflow into a collection
chamber.
It does not appear to my novice eyes that the bubbles are of a very
small diameter as currently designed. One modification that occured to
me is adding a airstone near the top of the tube where water is
injected over the bioballs. I really do not see how this modification
would be harmful.

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I wanted to report on the modification that I made. I purchased a
Profile 9500 air pump. It does not give a volume of air pumped on the
box, but it was largest and most expensive one at petco (30 bucks). I
drilled a hole big enough for air tubing to fit into near the top of
the tube where water is injected into the bioballs. I inserted the
airline tubing through the hole I drilled, and into the tube where
water is injected. I attached a corallife 3" limewood airstone onto
the end of the airline tubing, and placed the airstone about 2 1/2"
below where water is injected into the tube. The Profile 9500 air pump
is a dual output pump, so I used a "T" to combine the outputs into a
single output to the airstone. The total length of the injection tube
is about 24" I then adjusted the input water flow and the output water
flow to get a nice bubble column. As a first test I did not add the
bioballs back. My first observation was that the bubbles travelling
through the injection tube did indeed appear smaller. Further I did
not observe very many larger bubbles entering the upward reaction tube
as I did previously. It is interesting to note that even with the air
pump off, the skimmer did generate significant bubbles without bioballs
just through the action of the water being injected at high velocity
into the downward reaction tube. It was very clear however that with
the air pump on, the volume of bubbles, and the percentage of very
small bubbles appeared to increase.

Now for the amazing part. After ONE HOUR, I have obtained more dark
green skimmate than I have previously gotten in several days. This
modification really doess appear to have made a huge improvement in the
efficiency of the skimmer. I will update in the coming days, and will
be testing my phosphate levels to see if I can see a drop in my
phosphate level.

[Mislav]

Nice idea taegu.

I'm thinking that the reason why you don't get fine air bubbles with
downdraft only could be in the pump supplying the downdraft. It is really
important to have pressure rated pump to eficiently run downdraft. The
reason could also be in too much/ too little bioballs.

Mislav

> wrote in message
oups.com...
>I wanted to report on the modification that I made. I purchased a
> Profile 9500 air pump. It does not give a volume of air pumped on the
> box, but it was largest and most expensive one at petco (30 bucks). I
> drilled a hole big enough for air tubing to fit into near the top of
> the tube where water is injected into the bioballs. I inserted the
> airline tubing through the hole I drilled, and into the tube where
> water is injected. I attached a corallife 3" limewood airstone onto
> the end of the airline tubing, and placed the airstone about 2 1/2"
> below where water is injected into the tube. The Profile 9500 air pump
> is a dual output pump, so I used a "T" to combine the outputs into a
> single output to the airstone. The total length of the injection tube
> is about 24" I then adjusted the input water flow and the output water
> flow to get a nice bubble column. As a first test I did not add the
> bioballs back. My first observation was that the bubbles travelling
> through the injection tube did indeed appear smaller. Further I did
> not observe very many larger bubbles entering the upward reaction tube
> as I did previously. It is interesting to note that even with the air
> pump off, the skimmer did generate significant bubbles without bioballs
> just through the action of the water being injected at high velocity
> into the downward reaction tube. It was very clear however that with
> the air pump on, the volume of bubbles, and the percentage of very
> small bubbles appeared to increase.
>
> Now for the amazing part. After ONE HOUR, I have obtained more dark
> green skimmate than I have previously gotten in several days. This
> modification really doess appear to have made a huge improvement in the
> efficiency of the skimmer. I will update in the coming days, and will
> be testing my phosphate levels to see if I can see a drop in my
> phosphate level.
>