Habitat size for Ivan?

I have had my Russian tortoise Ivan for about a month now and he seems happy and healthy. He eats well and already seems social with me! Since I have a cat who likes to hunt and a clumsy clueless dog I decided the only safe way to house Ivan was a tank (even thought I know you guys don’t like those a lot). I just want to check if his “house” is big enough for him. Btw I have all the proper lighting also. Thanks! Also I believe the dimensions of the tank are 48 wide, 12 tall and 18 front to back

Nowhere near, sorry. That ramp is a huge tipping hazard. You are going to need to stop him climbing that and falling off.

Ivan needs 4’x8’ minimum floor area.

Please read and act on these care guides:
They're written by species experts working hard to correct the outdated information widely available on the internet and from pet stores and, sadly, from some breeders and vets too.

Beginner Mistakes
http://www.tortoiseforum.org/threads/beginner-mistakes.45180/

Russian Tortoise Care
http://www.tortoiseforum.org/threads/russian-tortoise-care-sheet.80698/

Hello, Ethan, and a very warm welcome to Tortoise Forum to you and Ivan.
You are quite right to keep the tortoise safe in it's own enclosure, but there's nothing wrong with tanks, they make great enclosures, the trouble is getting them large enough.
Joe's Mum is right, a Russian tortoise needs as much space as possible to roam, explore and exercise. They need to walk about a lot in order for their digestive system to work properly.
I'm afraid 4' by 8' would be an absolute minimum.

Ok thanks!

I can't imagine trying to house a russian tortoise indoors. They require so much room, it's just not feasible indoors. It's so much easier to have them outside then allow them to hibernate when the weather gets too cold for them to be outside. I've had a few rescued russians here at one time or another, and my indoor quarantine enclosures are about 4'x4'. Those darned russians just scrambled, climbed, dug the whole time they were in there. I couldn't find people to adopt them fast enough (to suit me)! So glad to place them and get rid of them!!

Your dimensions are 48" long by 18" wide, so you could buy another enclosure just like that one and put them together end to end. That would give you 8' x almost 2'. I think you could get buy with that.