I grew lettuce with the ebb & flow technique last year using Perlite. I ran my pump for ½ hour 4 times daily & it did well  even with the summer heat. The cycle should not be more than ½ hour. My deers tongue, romaine, & lolla rosa did the best. I had problems with keeping the algae down on the Perlite, however, which near the end of season contributed to pests.

Thanks Baci. I did notice green alge starting to grow on the Perlite.
Also because it gets warm here I'm thinking of using a mist cooling system to keep the temperature down around the plants. Any thoughts?

If I used Perlite again I would use a fan - it would also help keep pests away. It gets very hot in my area & I did spray the lettuce daily with a mist. The Perlite has good moisture retaining properties & I did not have problem with the lettuce wilting. I also flushed my system daily - I might be wrong on that but I read somewhere that lettuce needed to be flushed frequently to decrease the salts. The lettuce looked great the majority of the crop - no burned edges or spots. I grew several varieties & the deer tongue & a red romaine did the best in my heat.

Hi. Using a fan is a great idea. I'll have to think about this a bit though. I can see how things can get complicated real quick. I got a timer and pump for the flood and drain, a faucet timer for the mist cooling setup, and a timer + speed control for the fan. Hooboy.

You can try the mist setup without the fan if you have a good breeze/ventilation near your plants. Just watch & see how the plants do.

Sounds like good advice. I'll start with a mist system first. In another forum I stumbled across a fairly cheap mist system consisting of a Melnor 3060 timer and the Arizona Mist Pro Kit. Going to give it a try. Thanks Baci.

The reason to use a fan is to encourage transpiration and plant growth when plants are planted densely or in a place where they won't get natural breeze.

The fan/speed control/timer will be the next component I'll be adding after the mist system. After that I'm thinking of using a SmartHome PowerLinc controller to control all the electrical components. The SmartHome Manager Plus software look very flexible and once programmed sequences can be downloaded via USB to the controller. Oh, and is anyone aware of instrumentation that can sense EC, pH, and Temperature remotely via RS-232 or USB link? Whew, thanks.