Direct answer 1/4 should be fine.. but depends on ur light type, sump capacity, power heads capacity and the seat they generate. There are some calculations on web or even in sgereefclub web page.. you can use for reference.. it’s always better to use one step more than actual capacity... I was using aircon to test and it was great.. I would still prefer aircon because most of the time it’s on and constant temp of 25 C. No point running 2 systems because chillers generate heat and add to ur aircon load so I am sure double power consumption.. will check my EB bill after running a month. Sent from my iPhone using Tapatalk