imo he will prob only get a foot in a 75 and stop growing and be stunted, so as soon as you can get him into that 200 do it, it will be worth it. why not just put him in the pond instead tho?? can we see the pond?? it will be alot warmer by the time he outgrows the 75 so he should do great in a pond. he will color up alot better as he grows too, looks good tho.