I have to agree with Big clown I think you have been provided with a variety of options here. Although if selecting ballast units for an aquarium hood I would use ballasts that are IP67 rated so that I could have the option to fit within the hood and to my knowledge only Arcadia provide IP67 rated T5 Electronic ballasts in T5 and T8s (limited ballast for T8 sizes though). They are also a forum sponser so you kill two birds with one stone, (if you get them from ALF, (forum wholesaler sponser) or a (retailer sponser) three birds.) 🙂