surface film problems (fwd)

Forwarded Message from aljem3 at attme_cnet.att.com (James E. Morehouse):

A friend without access to this list is having a problem with a 'whitish' 
surface film on his tank.  Looking down from the top its barely visible, it is
noticable looking up to the surface from the sidewalls.  When he skims the 
film off so that its a little more concentrated, it tends to clump.

Tank conditions:  125 gal FW, very few plants(for now)
                  dH 4, GH 5, temp 78, ph 6.9
                  manual co2, 2 6' VHO flour lts 
                  heavy fish load
                  UGF and 2 aqualclear external boxes
                  coarse gravel substrate
                  no fertilization (I'm working on him on this!) 
                  25% water changes weekly
The 'scum' appeared before he added the co2 and VHO lighting and has 
persisted.  He is getting ready to add more plants (saw the setup I have as a 
result of the info on this group and the Krib articles) but would like to 
clear this up before he adds.

Some recent posts have mentioned cyanobacteria and possible ties to excessive 
levels of phosphates and related the phosphate levels to feeding 
liver/beefheart based foods. He's fed a meat-based paste for years and never 
encountered this problem in the past. Is this surface film likely due to 
cyanobacteria and if it is, any suggestions on reducing the phosphate level ? 
 (the water changes don't seem to have any effect).  He's looking for a 
phosphate test kit now, any recommendations on brand and 'acceptable' levels?

Any clues as to what this is, how it may have come about and how to get rid
of it?

Jim Morehouse
Lucent Technologies (fondly remembered as ATT Microelectronics)
aljem3 at attme_att.com