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I've had my turtle since i was about 10. I'm 16 now and since then I have began taking care of it completely solo without the help of my mom. I always thought I did a good job but I slowly am realizing I might not be. I saw my friends turtle's shell and its a lot greener then mine was and just looked better, so upon some intensive googling, I think my turtle might have a bad shell condition. I don't think it's rot because its not soft and there is no tissue exposed. The scutes are falling off which I read is actually normal. Basically the turtle has white/golden-brown spots on its shell.

Also, my turtle is not very social with me, I mean, it practically tried killing me when i took it out of the water to take a pic and when I tried determining its shell hardness, how can I slowly bring it along?

Wow, that looks like some mineral deposits and some algae and some long needed shed. You could try brushing the shell with a soft toothbrush to get some of it off. Does he have the right basking lights? UVA and UVB.

Also, your tank is waaay too small for a turtle that size. He looks to be 6''-8'' so he should be in a 60-80 gallon tank at minimum. The rule is 10 gallons per 1 inch of shell.

I don't know much about shell issues, but it just looks gunky to me. Do you have a proper basking area with UVA and UVB lights? You should really check out this page:

http://www.redearslider.com/index_habitat.html

A good habitat and proper nutrition are the keys to a healthy shell. Read up on habitat, basking/lighting, and nutrition on the main site. It's really helpful. Can you let him dry off completely and show us a picutrure of his dry shell? He might have some fungus issues going on. It may just be air trapped under shedding scutes, which is normal; it can be hard to tell from a wet shell picture.

Are you using a UVB lamp along with a heat lamp? I can't say for sure, but it looks like MBD (Metabolic Bone Disease). UVB light, a proper diet with calcium supplements (cuttlebone) will help his shell.
The water level looks way too low for a turt that size. Get one of those suction cup type basking ramps and fill it up so he can swim around!

Water temp should be around 76F, basking area about 90F. A 5.0 UVB lamp should be set up about 12-15 in. above the basking area with no covers or screens in the way....

A good setup and diet may make your turt a little less grumpy.

definitely agree on everything grey goose said.

maybe try live feeder fish? my turtle is always a good mood when i drop a few in. plus he loves chasing them..and it's good exercise!!

looks like mineral deposits..may want to check the pH level with those pH strips.

but def lightly scrub with a toothbrush and some salt. salt can help kill bacteria and is the least toxic.

It looks like your turtle's shell needs a gentle cleaning for starters.

Basking under proper lighting (UVB and heat lights), and getting some natural sunlight would help the shell a lot.

I don't see MBD---the gap between the scutes looks like growth with retained scutes on it to me.