I am looking to get a new enclosure soon for my bearded dragon. I currently have a 40 gallon for my 6 month old and she is growing fast so I have been looking for a new one. I have found some great deals and I know 55 gallon should be the minimum for an adult but is there a maximum? I have found ones that are anywhere from 75 all the way to 150 gallons for not too expensive! Just let me know!
True 55 gallons are actually a bad choice for adult beardies, because of the narrowness of the depth, they're only something like 13" deep, the minimum for an adult beardie is actually a 40 gallon breeder tank, which is actually 36" x 18" 17", which is fine for a dragon about 20" or under, but more room is always good, specially if they're longer than 20".
to answer the actual question, about enclosure size, no I don't think one can be "too big", they can be excessive for sure, but I don't think it'd ever be "too" big as long as you could still maintain proper lighting and heat.