Fw: scum on surface

> From: paul lesniak <plesniak@ compusmart.ab.ca>
> To: aquatic-palnts at actwin_com
> Subject: scum on surface 
> Date: December 20, 1996 11:14 AM
> Hello everybody,
> 	Merry Xmas to you all and may you have a safe holiday season.
> I have noticed over the past month and a half(the tanks only been set up
> for 6 weeks or so)that 
> whenever I do a water change a couple of days later a surface layer of
> forms on the water.
> after a couple of more days the layer begins to dissapate and then is
> completely gone. I think I have heard someone else mention this, but I
> don't recall an answer or solution to the problem
> 	My tank details are as such:
> 			130g freshwater
> 			heavily planted with Hygrophila, valisnaria, Various species of
> Echinodrus
> 			Bacopa, Aponogeton Rigidifolius, even some lagarosiphon.
> 			Ph-6.8-7.0
> 			CO2 injected
> 			KH-5-6
> 			24-26 degrees C
> 			about twenty fish
> 			2-175 watt MH for lighting
> 			3"-5" 0f 3mm substrate
> 			Terrapur in the substrate 
> 			Fetrivol 13%(from germany) in a liquid form for the water
> 			Fe-.1ppm
> 		When I do a water change I nuetralize the chloramine with Fritzguard
> I also 
> 		add some HCl(Hydrochloric Acid) to bring the Ph from about 8.2 down to
> 7.0 in the
> 		water change water.
> 	Any suggestions as to what this "scum" is or what I can doe about it.
> could you comment 
> on the use of HCl in the Aquarium(I haven't seen any ill effects to
> 						Thanx,
> 							Paul. Lesniak
> 		P.S.-and a Happy New Year!!