re: surface scum

>From: aljem3 at attme_cnet.att.com (James E. Morehouse)
>I'm posting this for a friend...he has a 125 gal that he's had established for
>some time with 2 aquaclear externals and UG filters w a (relatively) coarse 
>gravel substrate.  He has just started to get the tank 'plant-ready' with the 
>addition of VHO lighting and CO2.  Just prior to adding the above, he noticed 
>the appearance of a thin surface film, whitish in color.  He's not aware of 
>any changes that were made that could be tied to the appearance and the tank 
>has been operating (with a fairly heavy fishload and no plants) for about 2 
> I noticed a 
>recent post (on phosphate) where someone (Dave?) mentioned that feeding with 
>high meat content foods could increase phosphate levels...I know that Gary 
>(the friend with this problem) has been feeding a homemade mixture using liver
>or beefheart in rotation with other foods for years..can this be a cause?  he 
>does 25% water changes weekly.

Prior to building my trickle filters (now settling tank systems), I had this
problem too.  It didn't matter if I fed flakes, bs, discus formula, or
whatever.  I don't know exactly what caused the problem, but I suspect it
involved a bacteria, protein, and calcium (I got hard water deposits as well).
It may have also been due to a fat and/or phospholipid buildup.  All of this is
pure conjecture.  I have no idea what it was, I just learned what to do to
eliminate it after a while.

When I installed my first good surface skimming overflow, I was surprised to
watch (from below) all of the scum on my water's surface quickly break up and
zip down the drain.  I've never had a problem with surface scum since unless my
filtration system shut down temporarily.  If the filter shut down, I had scum
pretty quickly.  I also had a phosphate problem, probably because of the meat
content of the Discus Formula that I fed.  According to my high-school biology
class from way-back-when, cellular membranes (animals and bacteria) are
primarily composed of phospholipids.  Cell walls (plants) are primarily
composed of cellulose.

I only had this problem when I configured my tank for plants (eliminated the
air-driven UGFs).  I suspect that the splatter from the air bubbles popping may
have helped cake the inside of my hood with the scum and reduce its impact on
the water's surface.

I don't have any surface scum on any of my tanks now, but I have surface
skimming water management systems on two of them, and my micro only gets fed
once a week.

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
(214) 575-3443 (voice)  MSGID:       DAWB
(214) 575-4853 (fax)    Internet:    dwebb at ti_com
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