salt residue and green scum

Question
hi lynda
i have a "typical" fresh water community tank. 55 gallons and well filtered and definitely not overstocked. chemicals are tested weekly and everything is in balance. water is crystal clear. i add salt to the water in accordance with the instructions.
this is my problem.
there is a white residue on the outside of the tank covers and on the filter covers; and there is this green scum on the glass under the light boxes.
i dont think i am adding too much salt...should i be using salt at all?
and what's causing that scum...and how can i keep it from happening?
thank you very much for your time and expertise.
alan


Answer
Hi Alan,
White residue is mostly caused by the PH.  If you have a high PH, this could cause white scum.  Green scum under the glass is caused by the lights.  The only thing you can do, is keep your glass clean.  Wash it off with a paper towel whenever you see there is too much green on the glass.  I always use salt in my tanks.  One teaspoon to five gallons of water.  Salt is not the problem.  Check your PH level to see how high it is.  Some fish live in Alkaline water, and some don't.  I do not know what fish you have, so I cannot comment on the PH you are keeping.  If you have African Cichlids, they need a PH of 7.6-8.0 ..If you have South American Cichlids, they live in acidic or neutral water.  There is little you can do for white scum, or green on the glass except wipe it off.  If you have fish that should be in neutral water, adding driftwood to your tank will help bring it down, but you cannot keep fish in neutral water that belong in alkaline water.
Hope this helps
Lynda