Strip lights can be fitted into the cage inside a mesh metal "cage" (perspex works too, just be sure the bulb doesn't give off too much heat as it could melt perspex) and if you go into any pound shop (99p stores, poundland, etc) and look for a shower head with the metal hose, the hose can be removed and used for trailing the wires across the top of the cage and out of it so there is no way the degus can get at them (I suspect that putting a little tea-tree oil along the length of the wire will also dissuade them from even considering having a nibble). However, I am not sure how degu-safe strip lighting is, and hopefully someone else with more knowledge could advise about the types of light it would emit. Degus are sensitive to UV light of certain frequencies, and I believe that strip lights give off UV light of a different frequency to normal bulbs. LED lights are a definite no-no unless you definitely get the right ones. I'm not sure of the details here, I just know the basic facts :-)
And you can be forgiven for not knowing this, there's a lot about degus that only a few people know and there is most definitely a lot I still don't know...I was reading a post in this forum yesterday about herbal remedies for degu illnesses and it has really interested me...we could deal with a lot of our degu's problems with natural remedies we make ourselves from stuff bought cheaply in a health shop or even grown at home :-)
If you decide against having the light on 24/7, have her food bowl (if you keep it in still, at least with a little bit of nibble food) and water bottle close to the house...she will learn to find them in the dark over time and the least distance she has to travel the better. As I said, 24/7 lighting isn't a great idea for degus, and they won't really need it on when they're asleep...esp. the brightness of strip bulbs :-)
If you got them that long ago, it is very unlikely to be pregnancy fat. It is also normal for one degu to be bigger or smaller than the others, but to have gained weight since then...well, I would aim to get her down to 280g again and 300g at the very least. Once you get her to reach this target weight, decide for yourself if you can "weigh" her by looks alone or if you should check her regularly to confirm she's keeping the weight.
The running ball is a good choice if they have nothing else, but if you give them time out in the run I don't think it'll make much difference...most of these balls are coloured plastic too, so they can't even see where they're going properly, which will be even worse for her if she has the cataracts. On top of that, they like to explore when they're exercising, it's not easy to sniff around through the plastic.
Consider making exercise time their veg time as well, you could put some herbs down on the floor for them to find by scent alone and you could just hoover up the floor afterwards. The rabbit run is good to give them a bit of exercise but they would probably need to be out in it for hours and hours regularly running to get enough exercise if she isn't running in her wheel.
I think it is safe to assume from what you've said before and in the last post that there is nothing in her current environment that is causing the cataracts, and it is probably also safe to assume she's diabetic from the treatment she got from her previous owner.
If you want to go over-the-top a little with dealing with this, buy some testing sticks (ebay has them, they're "bayer"-something, I can find the information if needed but it's on the forum too somewhere) and test everything she comes in contact with in a solution of water (would also mean you could test her urine and be 100% certain of her diabetes). By this, I mean turn everything into a water solution (so put a few P@H nuggets in water and mix it up until it's a thin paste, put some timothy hay/herbage/substrate into a blender with water and I mean separately rather than mixing the three up, etc) and test each one for the presence of sugars. Also test the water itself directly from your tap, it's not uncommon for small amounts of sugar (and various other unwanted minerals and such) to get into the water supply especially if you have a tank rather than direct supply. If you think your water may contain even a small amount, it is overkill to do so but consider trying bottled water for them. Also, let tap water stand (be allowed contact with the air) for a short while in a bucket or large cup before you put it into their bottle, this dechlorinates the water and makes it cleaner than before...shouldn't make much difference to the sugar issue, but should make for healthier degus. If you decide not to go through the hassle of testing everything she has, it's understandable...it is a lot of hassle...just remember you have to limit any other sources of sugar, which I assume you're already doing anyway. A lot of this is overkill, I'm just suggesting it for if you have the time and inclination :-p
I wouldn't consider bedding hay to be a problem fat-wise, if she's been eating that the only worry is the health aspect regarding hygiene and if her or the others have been using it as a toilet. All unprocessed foods (even hay) will contain a trace amount of sugar, but unless she's been eating the floor clean it shouldn't be a problem.
For now, steer clear of tomatoes unless you are going to make sure she doesn't get any (and would you even feel comfortable depriving her of something? Better to deprive them all of something they've never had, I think). Also limit her carrots (I mentioned carrots above) as they have a high glycemic index, which means the amount of sugar released from carrots is high...however, this does not mean carrots have a lot of sugar in, the carbohydrates in carrots are broken down a lot quicker than other vegetables so it gives a small sugar rush (information taken from
www.carrotmuseum.co.uk/nutrition2.html#Diabetes ). She can have carrots often, just in small amounts because of the amount of sugars released at a quick rate.
Builders sand would make an excellent dustbath if it wasn't for one thing...the word "dust" is there for a reason, and the chinchillas and degus require this dust to stick to the oils in their fur and on their skin for the cleaning to actually occur. Builders sand would have dust in it, but it is generally not the kind of dust that would soak in oils...chinchilla dust is sepolita, a form of clay, and we all know (at least we do now, looking logically at it) that clay is more absorbent than glass (most sand is either the type that is used to make glass or is fish droppings from coral-eating fish so is actually tiny pieces of coral...I'm not sure of the absorbency of coral, but considering that sand is found by water in beaches and it doesn't absorb the water and coral is found IN water I wouldn't rate them very highly in absorbency). Obviously, you already knew builders sand was wrong, I was just posting the reason for why in the highly unlikely event that the previous owner comes along and reads this forum, or on the offchance that someone else here thinks builders sand (or any type of sand, the word "dust" in dustbath is there for a reason) is adequate for degus :-)
Is it possible that while out in the rabbit run she found something on the floor (carpeted? tiles? If carpeted, it might have been hidden) and ate it? One little treat is unlikely to have caused diabetes, so this is just a hypothesis and possibility, but one treat might have "inflamed" it and caused her cataracts to return. If you have them on carpet, it might be worth hoovering the area before they go down. It's possible that if you have kids then they've had their breakfast or sweets and something's spilled or gone onto the carpet and not been noticed as it's gone into hiding until hoover time then the degus went out before it was hoovered...although something that small wouldn't have a great deal of effect on her, as I said above it's just a hypothesis :-)
As for her skittishness, try to associate her coming out with treats and give her a treat (preferably something not fattening or sugary, of course, unless you've got her over the weight issues by then...you mentioned aromatic crunchies, red balls and yellow stars, right? They should do perfect as a treat, all mine either like one or the other) every time she climbs out onto your hand or arm. Over time she'll automatically associate getting out of the cage with good things even if you don't actually treat her each time, although I'm not suggesting you stop treating her for it :-)
My three girlies are very skittish, but over time they have got more and more comfortable with me and the flatmate...they still are very wary of us at times, but they will climb out onto my hand and run onto my shoulder at least for a little while before they jump down and escape. I haven't done anything to get them to be more comfortable, just spent time with them and given them treats (sunflower seeds usually)
