im using arctica 1/3hp for my 4 footer
my total water volume is app 450l
lights on(8 x 54w), it takes app 75mins to cool 27.3 degree to 26.7 degree
resting time is also app 75mins
lights off, it takes app 60mins to cool 27.3 degree to 26.7 degree
resting time is app 120mins
based on these info, you might want to consider compressor instead