i could get one which was 24 high but the problem is i have a shelf with all my tarantullas on above the frog tank and at the moment they are in a 12 x 12 x 18. if i went to 24 inch high i wouldnt beable to get the light on top as the shelf would get in the way. so do you think that 18 high isnt tall enough? they wil be getting more floor space tho.