RES shell problem?

Question
I purchased 2 red eared sliders 6 months ago and both were about the size of a 50 cent piece. For now, both are in 1 20 gal tank which is 1/2 full w/water, has heater, basking lamp/area and filter. They seem to get along just fine w/no fighting. Not sure of sex; was waiting to see difference in claws and base of tail. This hasn't been possible yet as 1 is about 1.5 times bigger than the other. At first I thought the bigger must be the female(I read girls are bigger). But it's starting to just look fat, esp compared to the smaller. There is much more space (proportionally)between the big turtles shutes on its shell than the space I see on the little one. I felt it w/light pressure to make sure there were no soft spots and there weren't. Almost as if its growing fast than its shell.Are the shutes supposed to be tight together on an adult or will there be this space I see on mine? Just wanted your opinion on this. They eat 2x day due to age. They get (apprx) pellets 1xday, leafy greens every 2 days, blood worms 1xweek and shrimp or krill every 3 days or so. Quit giving guppies over a month ago b/c the big one kept getting bigger.  Any advice is greatly appreciated.  Thank you!

Answer
Hi Lisa,

I'm not an aquatics expert, so I don't know how much help I can be on this one.  If you could post a very clear picture of your turtle's scutes that would help.  It sounds as though your turtle may be pyramiding.  Are the scutes raised or bumpy at all?  Here's a link to what pyramiding looks like in an RES:  http://www.redearslider.com/forum/viewtopic.php?p=8716

I would cut feeding to once a day, and once a week skip feeding your larger turtle.  RES will always act hungry, so don't let them fool you into feeding too much.  Offer some greens every day (especially high calcium ones like turnip, dandelion, or collards), and trying varying the animal protein more (add boiled chicken or egg, earthworms, crickets, etc.).  Pellets are OK, but as part of a varied diet, so you might want to cut back on those a bit.  Put a piece of cuttlebone in the tank so they can self-regulate calcium intake.

The pyramiding won't correct itself, but if you're careful it won't get worse and the shell will look smoother over time.  You'll need to get a larger tank soon, too.  Also keep an eye on the smaller turtle and make sure it isn't getting bullied by the bigger one--not basking or eating enough, etc.  This is pretty common when one turtle grows faster than the other (and the bigger turtle may be hogging the food).  You may have to feed them separately for a while.  

Here's a good website (there's also a forum) on RES care:  www.redearslider.com.  Good luck with your turtles!