Hi again Leon,
Sounds good to me, the
nutrients developed at the university should do fine as they have figured it out and tested it for some time in local climate and conditions. It may even be better suited than some commercial product that is several times more expensive.
Same here for the timer, - but I guess your setup needs some 5-10 minutes to fill up anyway. You may reduce
pump size to delay the filling time close to 15 mins. More important is to find out and adjust the ideal cycling time. You need to allow time to drain and "rest" but not wait until drying out.
Hint: do not use too much coco husk. It truly retains humidity and salts. I am in fact using a mix of mainly rice hulls and little coco, plus pea sized gravel with my tomato buckets. I'm not exceeding 15% of coco. With this mix my toms are doing fine and I have got a pretty stable PH.
PS: In case you need more fittings and can't find any at your place, we have got a manufacturer here in Thailand that produces PVC and PE fittings in 16, 20, 25 and 32 mm, sprinklers, hoses, sprayers, you name it they have it. They are of good quality have ISO 9001 standard and are very cheap. Contact me in case you want me to help out.