Hi Lily,
Thanks so much for sending the photo. You've put some nice things in that vivarium (rocks and other things to walk round and climb over), so that will provide him with interest. But there are a couple of things I would change.
First of all,and sadly, vivariums are not good environments for tortoises at all, because it is really hard to get a good temperature gradient in the viv, which is important for them (it should be about 30C directly under the lamp, and then about 20C at the cooler end -- so that is about 10C difference between the warm and the cool ends). When you are measuring the temperature, are you measuring it directly under the light at the height of the tortoise's shell? That is essential because a thermometer on a nearby wall will be giving a much lower reading than it actually is. Also vivs tend to be high, but not so much floorspace, so they are great for lizards and snakes who climb, but not so great for tortoises. We get lots of people who have been sold vivariums by pet shops and it is a great shame because they can cause damage to tortoises. But as long as you have it, there is a fairly simple way that you can adapt it. As a minimum measure, take the doors off and put a board up across the front of the viv (or open one door fully and do the same. The board should be just high enough that your tortoise can't climb out, and that will allow air circulation and a good variation in temperature. Better yet, many people adapt them by taking the doors off and sitting the viv in a large 'tortoise table' which allows the tortoise to come and go. Here's a photo of what I mean:
[attachment=0]Viv conversion.jpeg[/attachment]
Secondly, I would change those pellets for a soil/sand mixture, which is more natural and better for the tortoise. Those look like alfalfa pellets, and they are edible, and very high in protein, so if he is eating them then that could be the cause of him growing too quickly. The best substrate for tortoises is one that closely resembles what they live in in the wild, which is a sandy soi, so we mix together sterilised topsoil and children's play sand (bags of both can be bought at garden centres, Homebase, etc.). Most people mix it 50/50, but my tortoises prefer more soil, so I mix mine about 60% soil and 40% sand. And then you give it a light spray every couple of days to keep it from getting dusty. And make it as deep as you can because they do like to dig into it.
The things you are feeding him are fine, but do you have access to a garden? He could do with more weeds, like plantain, sowthistle, or garden plants like campanula, pansies, etc. You can always look up a plant on our database to see if it is good to feed, and you can use our filter tool to make list of good plants.
He does seem to be growing a bit fast. What you want to aim for is slow growth, so we aim for between 1g - 4g per month. That is just an average, and some months he will grow more and some less, but if he is growing faster than that, then you need to cut down on his food. Because he is indoors all the time in the vivarium, he isn't getting as much exercise as he would if he had an outdoor area, so probably less food is better.
Tortoise love fruit, and in the wild they will occasionally encounter fruit that has fallen on the ground, but it really isn't good for them because their digestive systems don't cope will with the natural sugars in fruit (and tomatoes count as a fruit). The odd treat won't hurt him, but it isn't necessary. Cucumber, however is good for hydration because it has a lot of water in it, so on hot days that is a good thing to feed (but I would peel it because many supermarket cucumbers have been sprayed with insecticide. That's great that you are providing him with a cuttlefish bone, as that will provide extra calcium.
Your UVB strip light is fine, but you should really put a reflector in it, as the light can damage your eyes if you look into it. Reflectors don't cost a lot and just clip right onto the light, so easy to fix, an they also reflect more of the light down towards the tortoise, which is good. Looking at the light through the glass on the front of the viv won't hurt your eyes, because UVB doesn't pass through glass, but when you open the top and look down at it then it isn't good for you. Also, those lights are only good for a year or two years at most and then need to be replaced, because even though they still produce light, the UVB isn't coming through any more. Without UVB the tortoise can't absorb and utilise the calcium in its diet, so it's really important to change the bulb regularly. UVB reacts with the skin to produce vitamin D3, and although the Arcadia supplements you are giving him are fine, neither had vitamin D3 in it, so it might be good to get a supplement that does, like Nutrobal (most pet shops stock it and you can buy it online). The best UVB is from the sun, so if you have access to an outdoor area, I'm sure he would love being outdoors during the daytime if possible, but if not then your 10% light should be fine as long as it isn't too old.
I'm so sorry to have gone on for such a long time here! I hope you aren't bored out of your mind. I can see that you really love your tortoise and have cared for him well, but I think in the beginning you weren't given good advice about housing or substrate, which is very common! I know I have written a lot here, but aside from altering the vivarium I hope it doesn't mean too much effort on your part to get his husbandry just right.
I don't know if you already have a care sheet for Spur Thighs, but if not here is a link to one (there are several species of SpurThighs but this sheet should be fine):
https://www.tortoise-protection-group.o ... 014New.pdf
Finally, to make up for my long and boring post, would you like a free copy of our Tortoise Observation Records booklet? It's just a way to keep all your records in one place -- growth (weight and length), change of equipment like lights, details of vets, etc. Just send me an email with your address to
nina@thetortoisetable.org.uk and i'll pop one in the post to you.
Nina