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Re: Biowheel venom and CO2 stripping

Bob Dixon wrote:
> In a message dated 98-01-17 15:56:43 EST, Roxanne writes:
> << One pet shop owner in Davis told me the Biowheel was a marketing 
>  scam and did very little useful filtering. >>
> The do very little MECHANICAL filtering, but then they aren't supposed to.
> They are strictly biological filters.  They work on the same principals as
> wet/dry trickle filters.  

I've always regarded them as a scam.  Harsh wording and all.  The problem 
isn't with the concept.  The problem is that the contact surface on the 
biowheel and the contact time appear far too small to me.  The contact 
surface in an actual trickle filter is much, much larger.

I don't use biowheels and never have, and I'm not saying they don't work
at all.  Lots of things work.  But, if you're in the market for an
over-the-back power filter, then it looks to me like aquaclears pose fewer
nuisance opportunities and provide more filter for the money. 


On a different subject, Bob wrote:
> In a recent thread on the Apisto List, someone said that air-driven filters
> strip CO2.  Any opinions and/or observations would be appreciated.

Any dissolved CO2 in excess of the 0.43 mg/l or so that's in equilibrium
with air under normal conditions will tend to escape into the bubbles. 
The smaller the bubbles (more contact area) the bigger the effect. 

In the water well business they sometimes use air lifts as a means of
getting water from wells before a pump is installed.  That method alters
the water chemistry so that water samples taken that way are of limited
value.  I recently had a driller sample a well using air lift, then repeat
the process with a sampling pump.  As I recall (I don't have the lab
sheets with me at home) the water sampled with the pump had a pH of 7.8. 
The water sampled with the air lift had a pH of 8.4.  The pH change
reflects the difference between low CO2 concentrations and very low CO2

Air lifts in aquariums should do a great job of removing CO2 (and a few
other things).  In fact, I'm not sure if there's any significant
difference between a stripping system that you would designed with the
intent to remove CO2 and an airstone-driven air lift.  Aerating with the
venturi on a power head should have a similar effect. 

You'd need to push an awful lot of CO2 into a tank to offset the 
stripping effect from a venturi or an air-driven sponge filter.  Even 
more to offset the effect of an air-driven UGF with airstones.

Roger Miller
In Albuquerque, where the weather is  "normal" -- Clear, dry, calm and crip.