@zalaman, your best PH point is around 6.0. Now I did say around so that means 5.8-6.1. Your plant won't affect the PH a first so make sure your good. I personally like 6.0 myself cause as you said different nutz are absorbed at different PH levels, and 6.0 is the sweet spot where they will get what they need. Check with the Coco boi's, if that's what medium your in, for high and low limits. So in other words don't go rushing in to adjust the PH till it has reached it's limit, either high or low. Let it drift all the way before making adjustments. I'm in DWC so I let mine drift from 5.5-6.5, I don't try and hold it at one set point, let it move and then you can read why it's moving. This is a good start and hope it helps.

@woodi2 very helpful and the chart. thanks im using coco coir btw!  

@zalaman So I run mainly coco, and I run either cannacoco or greenplanet depending on how much of what I have left at the time. For me I will start at 5.8ph, I will bring it up to 6.0ph for the first week after stretch and then up to 6.2ph from end of stretch and until harvest. I do it this way because it works for me. Ideally you want to be between 5.8 - 6.2ph through out the grow, the happy medium being 6.0 from go to woah. One tip I can give you is to keep an eye on the ph level of a standing rez, it is not uncommon to see ph fluctuations if a feed mix is left to sit over an extended period. I usually make enough feed up for a day or two and check ph quickly before I feed each time, it takes 2 minutes to check and saves the nightmare in case that ph has rocketed since you made the batch up(I find it more common to spike using canna than green planet, that doesn't take away from either of them though as they are both excellent nutrient lines and is just my observation). So really there is no exact number to be at as the range is more what your looking for, you want to shoot for a number in the middle if your unsure. If you want to play around with the levels a bit to tweak your run then I suggest starting at that 5.8 and moving up incrementally at different stages through your grow, keep a diary of how the plants reacted and then you can dial in your preference from there. Good Luck!   

Yer, I’m in coco and I’m using very similar practices to BubbleHok (no surprise again lol) in that I like to mix a multi day res. In an ideal world for me that res is a 2-3 day usage item and I try to stick with that unless I’m away for an extended period and I have to rely on auto watering. I start my ph at 5.8 and check it before every use (daily) only adjusting if it climbs above 6.3. If it needs adjustment I bring it back to 5.8 again. With 20% runoff from daily fertigations the plants find their happy place fairly easily. I used to chase that ph 5.8 constantly but now I work less and just chase the range of 5.8 - 6.3. If the grow starts to look unhappy I’ll tighten the range but it’s only happening very rarely these days. 

thanks for the the help guys very useful and informative. how costly is a auto watering system on a budget and what is needed?

@monkeydo can you take a look at my light? i know links are not allowed i got x2 off amazon and cost £45 each i dont think they are a true 1000w im unsure of distance with this and dont know if i should go with the manufacturer recommendations? just google or type this in amazon the uk site.

1000W LED Grow Light, Sun-Like Plant Light Full Spectrum for Indoor Plants

@zalaman, they made by Bloom Plus, it's a 336 Samsung diodes, 90.4 watts, flower foot print is 1.5'x1.5'/43x43cm. Sorry it not 1000w. I would still go by the manufactures recommendations as far as height and distance.

@zalaman sounds like Woodi was right on the problem and that info sounds right. The Amazon UK didn’t list the “actual” wall wattage and they also never said it was 1000 watts, only that they thought it was as strong as 1000 watt HPS light (it really isn’t). The deceiving trick is the advertising only says “1000w” and not “watts”. It’s a little dishonest because you are assuming watts from the “w”. Early on I bought some Philzon 600w lights, turned out they were 108 watts each. We all fall for this trick early on.