Hi in my system I built about 10 myrs ago, I used a fish tank
pump of about 18 watts and a normal timer with 15 minute settings. I set this to run between 3 times a day in winter and 5 times a day in summer. I have had some great crops with this set up, growing tomatoes, lettuce, cabbages, roses, chilli peppers, mint and parsley. I am using expanded clay balls for medium in 20 litre plastic oil tanks cleaned with the tops cut off. I often run a single pump cycle at night during summer to prevent drying out. In tauranga new Zealand temps range from light frosts in the morning in winter to about 28C in summer. My set up is on the back deck in the open.