Is it ok to feed my axolotls things from my garden?

Just thought I would ask this question because on the weekend my son very sheepishly told me, me caught a beetle and fed it to our axolotl. Luckily there seems to be no ill effects, though I have told them not to do it again!!
Any thoughts on this? Do you think it is safe to feed them non-poisonous bugs? Also slugs or caterpillars? Flies?

There was also a dead fly in our tank that the axolotl ate before I scooped him out

I'm sure the odd beetle features in their diet in the wild; same with slugs, flies and perhaps caterpillars. It doesn't mean that it's risk-free though. Some beetles have powerful jaws that could conceivably cause internal injuries, slugs can carry parasites and flies can carry bacteria from the nearest pile of poop or rotting corpse. It's not particularly uncommon for animals in the wild to be injured or killed when they eat things.

You also have to watch out for pesticides, ground that might be contaminated by preservative being washed off of a wooden shed or that's contaminated by oil from being beside a driveway and things like that when catching food in your garden. I put a new fence along the back of the garden last year and thought I might be able to use the clay I'd dug up when putting the fence posts in, but it was right beside the neighbour's driveway and the clay stank of oil and petrol.

I mostly feed my animals with worms that I raise in my compost bins, and my axolotls also get fish pellets. Worms are a very safe option, barring chemical contaminants in the area where you collect them, and they're also one of the most nutritious foods.

Also with worms it good to leave the in a container with wet tissue over night because they will excret any gunk in their intestine.

Great thanks for your replies.
I am currently researching worm farms, just trying to find out the best variety available in Australia that will be good food for the axies and also breed well.