ph drop very fast in RDWC.. help me!

kamikaza said:

Hi guys!!

i am growing 3 plants in RDWC sistem, 60L total of water.

strain: easyrider Autolower, day 65 from seed.

air temp: 75-86F

ventilation ok, RH ok.

water temp: 70-77. (no more then 72 lights on. at light off i shut down the AC, and temps climb)

sistem: 3 buckets of 4 galon, 3 galon of water in each. water level alweys the same, at half inch above the bottom of net pot.

all buckets conected to a central reservoir, 270 GPH pump, and come back to res by gravity.

RO water, GHE flora 3 part.

ppm: i tried 500 to 800, makes no sense.

additives: x-cel, rhizotonic, heisenberg tea. i tried with only RO water and mineral nutes, and with additives. makes no sense.

past problems: brown slime attack on first week. (in the 'veg station') i clean the water, sterilised the res using H2O2, and filled back with RO water and mineral nuts ONLY.

keept it thet wey for two weeks until i get the great white shark i ordered from EBAY to make the tea. i couldn't find GH AF EWC in my country, and shipping it by air from US whould coast me an arm and leg, so i used local humus instead. there is only one brand of it available here.

there was a tiny bit of slime at that period, i changed and clean the res every 4 days, and once i get the GW shark by mail i made the tea and problem solved.

had small calcium deficincy and P deficiency. nothing seerius.

no PH problems until day 36. stable, or shift slowly up.

from day 36 it started to drop slowly like from 5.9 to 5.6 in 24 hours, and get worse and worse.

now, at day 65, it drops 0.1 point in an HOUR. like from 5.8 to 5.3 in 5 hours.

and i have to use tons of PH up to corect it every few hours, thet change the nute balance in the water, raise ec, and force me to change res every 2-3 days.

the ph drop also at LIGHTS OFF.

i am still using the tea, but not at full dose, i only add to the tank 400 ML every second day.

what could be the problem?

bacteria? not right EC?

is the plants causing it?

i tried use different EC, 1.05 to 1.65, no difference.

tried with no organic material, only mineral nuts and RO water, no differnce.

i am thinking of strelise the water again with H2O2, and try with no organic material.

at what ratio should i use it? i only have 3% from pharmacy. can't get anything else.

should it be 17ML\liter? when i used it on my 9 days plants at 40ml/galon, (10ml/liter) one of them nearly died, and the others were shocked/injured.

is it safe now as they are bigger?

thanks for any help!


View attachment 2397785plants demaged from H2O2


roots at day 32-33:

View attachment 2397788View attachment 2397790


roots at day 41:

View attachment 2397795


and at day 51, 2 weeks ago. (they are too big now, so can't inspect the roots)

View attachment 2397801View attachment 2397803


and here they are today, day 65:

[video=youtube;zpKBjRy6mDk]http://www.youtube.com/watch?v=zpKBjRy6mDk&feature=youtu.be[/video]




thanks again!!

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Taviddude said:

Man, your plants look great. I'm really at a loss as to what would make your ph drop that fast. Try cleaning out the system again.
Also, check out your nutes, and see which one buffers your solution up. It could be that your plants are using the fuck out of that particular nutrient and as it gets used up by the plant it's ph up power gets used also letting the ph drop.
That's a WILD ASS Guess, but that's where I'd start personally especially if your plant has some mild nute deficiencies. It could just be sucking that shit up.

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mjjbabel said:

When is the last time you calibrated your ph pen?

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kamikaza said:

nitro harley, is your barrell conected to the buckets or just using for auto top up?

if the PH in the barell rise it may indicate bacterial activity in it, organic material being broken down by microbs.

the ph drop only at flower? in veg it goes up, and in flower down?

my system is outer reservoir thet constantly top up the buckets by the pump, and the water flow back to the res by garvity. so all the water in the system get circulated like 6-7 times every hour.

the ph/ec is the same at the buckets and the in the reservoir.

when using H2O2, at what ratio are you using it? when i used it at 40ml/galon on my 9 day old seedlings, it nearly killed them.

i have 3% H2O2 from pharmacy.

if i want to sterilise the res, should i apply it, wait 24 hours and then make a res change? or should i use it immidetly after res change, wait 24 hours and then inoculate the res with bennies\add organic additives?

i know it killes everything in the water, but evaporate after some time? how long? some people use it constantly in their set up.

if the roots are causing the PH to drop so vielontly, it's mean my ec is too high? so i shouled lower it to 400 ppm?
but i suspect it some kind of bacteria.

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