Discolored light ring

[TTnC4me]

3yo IG gunite, swg, exposed aggregate, 17,000 gal
1.5hp Hayward 2sp pump, w/cartridge filter & solar heating; non functional ozonator.

From this thread: http://www.poolforum.com/pf2/showthread.php?t=553
Ben stated if acid makes it fizz, then it's calcium carbonate deposits.
I have a build up of something on the metal ring around my light. I've unscrewed it and taken it out, poored acid on a sponge and when it contacts with the surface, it fizzes. Several months ago, I didn't have deposits, the ring would just turn black. Acid would easily wipe it right off, but no fizzing.

I just used Ben's kit and found out my CA is 520. I have NO IDEA why my Cal is so high!
Here are the rest of my numbers from PS233:
FC 4ppm
CC 0
TC 4
pH 7.8
Alk 70
Cal 520
Cya 0
Temp 88

I've added acid for pH which is usually maintained ~ 7.2 - 7.4, and stabilizer for Cya. A few years ago I went through the motions of draining my pool 1/4, then 1/2 but our city water is crap and it would only drop the level ~50. The lowest my Cal has EVER been is 430 last July. This is also the lowest my Alk has ever been. It usually hovers ~110, but I'm doing nothing different. I also have the slightest tint of orange on some walls. I bought some Metal out for that.

So, please tell me if my assumptions are right. The build up on the light is seemingly calcium? What would cause black to appear? The orange is probably metal? I should get my pH under 7.2 and my FC near 0 then add the metal remover, brush and reinstate chlorine?

Your insight is greatly appreciated!

[Simmons99]

You can determine if the orange ring is metals by crushing some vitiman C tablets in a sock and rubbing it on the stain - if it clears it is a metal stain - see the metal forum for additional info on it.

[Poolsean]

The black on the light ring occurs usually from electrolysis. Make sure your swg has a bare copper #8 bonding wire, or green ground wire attached to the chassis of the salt systems control unit.

just my 2 cents...