Flood and drain problems...

[HomeGrown24]

Hi all. Firstly I have been a fan of this site and it's many helpful tutorials since I started learning to grow hydroponically 2 yrs ago and has helped me a lot to learn the many things one needs to know to grow hydro weed so thanks for all the help you have given me.
My problem I have now is that my diy flood and drain system which I have successfully grown 2 plants with now has a problem I can't seem to work out and it keeps killing my plants.

Basically my flood and drain system is a 14 gallon tub as the res with a 8 gallon plastic bin set on top of the tub as the "plant tank". An 8" net pot, which is filled with hydroton and houses the plant, is set flush to the top into the lid of the plant tank. The waterpump is in the res which, via 13mm hose pumps nutrient water from the res and into the bottom of the bin and "floods" the bin when pump is on. Also there is an overflow tube (24mm hose) that runs from 3/4 of the way up the plant tank and down Into the res.
The plants are in veg on 16/8 and I flood them for 15 mins every 3.5-4hrs by manual timer when the lights are on and no floods when lights are off as that worked for me previously. The res e.c.is 1.5 (0.2 base included) and ph is always maintained between 5.9 and 6.2.
This system was working fine for me for a while but in the last few months every plant I start in them ends up dying.

I germinate the seeds in rockwool cubes in shallow nutrient water until the roots start coming out of the rockwool and all go's fine there..then I transfer them to the flood and drain system and they seem fine in there until the roots start emerging from the net pots as they eventually do..then the ends of the roots start dying from the ends back and look burnt and withered...the plant stops growing from there and eventually dies as I cannot work out what is causing it.
I have tried to grow 6 or so plants so far and all have died the same way.
I myself believe my system is flawed in some way but I may be totally wrong there..

I'm at the point now where I will have to convert to growing in soil until I can hopefully figure out what is wrong with my hydro system.
Hoping someone with more knowledge and experience than a newbie like me can help me figure out what the problem is because I prefer growing hydro to soil.

I've included pics of 2 of the affected plants, a pic of both the plant itself and its roots and a pic of my main growroom with all running in there.

I'm happy to answer any questions or give more information about my setup etc that I haven't already given if it will help.
Thanks

[Bluey]

An EC of 1.5 is way too much for a plant at the stage you are showing in those pics.

EC should be about 0.3/4 +base to start and slowly ramped up. You could start with bloom to encourage root growth and slowly phase in veg nutes. At that size Id be thinking no more than about 0.7/8 +base.

Are you using an anti algal in the mix? This is normally mandatory for a hydro grow.

Are you aerating the reservoir with an airstone? If not you should but it will impact on the pH swings. A start point that seems to be the go is 5.8 and then correct at least every 24hours.

I think your problem is your high EC, although your leaves aren't showing that. Check your pump for blockage and use a digital timer on the pump, not analogue. That can also run the air pump for the airstone. I would flood them during the dark period also to keep them from drying out.

Keep us informed how you go.

[HomeGrown24]

I've always started them on 0.8 e.c once the germinated seed go's into the rockwool cubes and once I transfer them to the flood and drain I ramp it up to 1.3 (- base) from there. I've read that u don't even need nutrients at that stage but they seem to like it and I've never had a seedling die on me yet at the rockwool stage.
I also add 0.2 of cal mag to the flood and drain res on e the plants get transferred to them, that is included in the 1.3 e.c.

Well I have 4 plants atm and ive transferred 3 of them to my 2 diy dwc systems (one houses 2 plants) to see what happens and hopefully save them. 2 of them the roots haven't begun to emerge. But after 3 days in the dwc roots are emerging from 1 of those 2 and looking white and healthy as they should be. The 3rd dwc plant seems to be recovering as it was one of the ones in the pics. The 4th plant is still in one of my flood and drain systems and I dropped the e.c.to 0.8. It's been 24 hrs since then and no noticeable growth or improvement..the roots still like bad like they did in the pics but will give it some time.

The weird thing is the plants look totally healthy while the roots are slowly dying but it almost completely stops growing and will continue like this until it starts showing nutrient deficiencies everywhere and all the leaves will slowly die off until I put it out of its misery. That's how it happens every time and it starts as soon as I transfer them to the flood and drain systems which is what convinces me it's my system at fault
To add the plants in the dwc's are still on 1.3 e.c. and ph 5.9 and seem to be enjoying it.

[Bluey]

My nute manufacturer recommends a start at 0.8 EC also but I have found this can pretty much just about kill my seedlings from nute burn. I only ever did that once

When I noticed that I halved the mix straight away and saved them but the damage was done and they were badly stressed. They never seem to fully recover from that but I did get a pretty good harvest with quality buds but yield was down.

It needs to be noted that's in coco but I am sure hydro is very similar re EC.

I've never been able to get to more than 75% of the manufacturers recommended strength without starting to introduce significant burn across half a dozen different strains from landrace sativa to strong indica traits.

I use 0.3EC in a aeroponics bucket with great results for cloning and can grow the clone 2ft high with massive roots without showing deficiencies or burn with a PPFD of 90 to 120. I mix in silica also at a similar low ratio.

I don't know what the correct or best frequency is for floood and drain but in my bucket I'll spray as often as possible only giving it a break so the temperature of the nute mix doesn't climb too high...between 3 minutes every 20 minutes and 10 minutes every 20 minutes depending on room or tent temperatures. I try and keep the solution around 21⁰C. Too high and it won't aerate as well, think oxygen saturation points.

Be worth checking your nute temp but it's not super critical, 17 to 25 should work fine.

So all I can think of is to maybe increase frequency a bit, keep that going through the dark period, same frequency and I would definitely lower EC also.

[HomeGrown24]

Well it seems that the high e.c. was the problem because 12 hrs after my last post the 1 plant I left in the flood and drain at 0.8 e.c started coming back to life. So I got rid of the dwc's and put the other 3 plants back into thier F n D systems at 0.8 e.c. as well and now they are all growing and new white healthy roots are slowly replacing the burnt roots on the bottom of the pots of all of them. They are all nearly recovered and growing strong after 3 days now so all good.
I guess because those e.c. levels had worked for me before I thought, being a newbie and not knowing any better that would work for all plants and wasn't the issue here when it was. Well I now know to start lower and work my way up by reading the plant. I'll stick to the levels you suggested unless the plant shows it wants more of course. Another lesson learned lol


So thank you for steering me in the right direction (and away from the wrong direction lol) and helping me solve this problem.