Habitat - Indoor :: Sand for my 2, 6 months old turtles. Need Tips

[Alphabet]

Hello,

So I have 2 RES, that are 6 months old. Blocks(female) and Bricks(male). I've bought them from the pet store 6 months ago, so I assume they're about 6 months old.
Ever since I've used an Incandescnet Bulb for their basking area with a UVB Bulb of 26 watts. This is the UVB lightbulb (http://www.exo-terra.com/en/products/co ... _bulbs.php)

This is the tank at the moment ( http://www.exo-terra.com/en/products/na ... _small.php ) I've used this for 6 months already, they seem to be fine. (shells are turning brown though.) I'm planning to buy an Aquarium of 50ish gallons and modify it to a Terrarium for them.

Since I've been using gravel since day one, I've done some research and read that gravel is bad, so I'm planning to buy sand ASAP, but my one concern is that, there are sand sold at the Hardware stores that's called "Riversand"
but the description states "mostly used for cement", I'm wondering if its safe for them.

Sumarry:
-Are my light good?
-Is the tank at the moment bad and should I upgrade ASAP?
-Are they lacking nutrients?
-Is the 50ish aquarium good enough?
-Is the sand safe?

Thank You,
Alphabet

PS: Im from Belgium, so our winters get cold and heaters automatically turn off at night.

[Alphabet]

So Ive visited the stores they said theyre 9 months old !

[Kansasslider]

I will talk with you about sand a little but im not sure whats available there? In the US,Play sand from home depot or menards is fine. You must! Rinse the heck out of it so it doesn't cloud up your water. Pool filter sand is better because its fine grain sand unlike play sand but either is fine. I like white sand and that's what's in my tank. I bought it at a pet shop and it cost an arm and a leg. Mystic White II pool filter sand is cheaper and I wish I bought it instead of aquraium sand. Any fine sand as long as its silica sand will be just fine. I like white but its up to you on color. Most regular sand is brown/tan in color. I'm not sure if my sand is silica sand or not? Probably not. But, my turtles don't eat it anyway so its not an issue. And it comes in lots of colors. Hope that helps ya!

[ljapa]

-Are my light good?
-Is the tank at the moment bad and should I upgrade ASAP?
-Are they lacking nutrients?
-Is the 50ish aquarium good enough?
-Is the sand safe?

The lights should be good for basking.

In the U.S., wild RES are primarily found in ponds or very slow moving rivers. Even the shallowest pond provides for much deeper water than any aquarium. I don't think the aquarium you have can provide for deep enough water for swimming. And a 50 gallon set up as terrarium probably won't either.

A RES should have water to swim in. You can use Rubbermaid containers instead of aquariums.

As to the sand, I'm not familiar enough to say if it is safe or not. I used pool filter sand for my aquarium. I would think that most sand is safe.

[Kansasslider]

River sand is silica sand and safe for turtles. Just remembered that