ppm keeps creeping up

Background:
I built what is essentially a mini continuous flow DWC system using 2x 5gal growing buckets and 1x 5gal res. 400gpm pump sends soup to the 2 growing buckets that fill via waterfall action and a raised drain tube (that allows me to easily adjust water level) drains much faster than it fills to keep water levels steady. DO is hopefully sufficient w/ the waterfall action, siphon drain, and continuous water movement, but I'm supplementing with some H2O2 for now just in case since I just transplanted last Friday. Seedlings are in rockwool cubes and surrounded by well-rinsed and pre-soaked hydroton media. Water level submerses the bottom layer of hydroton but is about 1/2" lower than bottom of the rockwool cube. Seedlings appear to be growing fine. Will lower water level once roots poke through bottom of net pot. Total water volume ~10gal

I've been testing ph and ppm daily (first time grow). I know pH will continuously rise as more CO2 is mixed into the water from the agitation (and the Ca buffers in the tap water), so I've been adjusting daily down to about 5.9, which will rise to about 6.4 the next morning.

I presume this is still the seedling stage, so I'm using between 100-300 ppm of nutes. Filtered tap water came in at ~240ppm.

The total ppl has been steadily rising about 80-120 per day. 1/1: 420; 1/2: 500; 1/3:580; 1/4:720. Water level has been consistent so it's definitely not evaporation, nor are 2 seedlings drinking the water. Res temp ~72 (working on lowering it). Is the submerged layer of hydroton adding ppm to the water? I did notice some clay "sand" in the res. wtf?

Problem/issue:
I don't think the pH is supposed to fluctuate that much, is it?
What the flying F is going on w/ my ppms?
 

rkymtnman

Well-Known Member
so total ppms are like 400 to 500 ish if i read that correctly?? that's pretty high IMO for seedlings.

your source water is gonna give you issues at that ppm level.

and adjust your pH to 5.5 and let it rise to 6.1 before adjusting down.
 
so total ppms are like 400 to 500 ish if i read that correctly?? that's pretty high IMO for seedlings.

your source water is gonna give you issues at that ppm level.

and adjust your pH to 5.5 and let it rise to 6.1 before adjusting down.
I always thought nute ppm recommendations are added to whatever water ppm was? So if I wanted 200ppm of nutes and my water was 200, then total ppm should be 400? What's weird is the rising ppm which I'm currently attributing to the hydroton (but not too sure).

I'll be swapping out the water in the res today since I'm changing the drain hose size and moving my pump to external to help w/ heat. ~3gal change.
 

rkymtnman

Well-Known Member
I always thought nute ppm recommendations are added to whatever water ppm was?
you are correct but with high ppm source water, feeding seedlings becomes harder. let's say your plants can only handle 200ppm: you have no "room" to add nutes.
maybe try RO/distilled water until the plants get bigger and can handle more nutes.

if ppm goes up, your feed is too strong. which will lead to nute burn which will lead to nute lockout and then plant death.
 
you are correct but with high ppm source water, feeding seedlings becomes harder. let's say your plants can only handle 200ppm: you have no "room" to add nutes.
maybe try RO/distilled water until the plants get bigger and can handle more nutes.

if ppm goes up, your feed is too strong. which will lead to nute burn which will lead to nute lockout and then plant death.
Ah, ok.

They seem to be doing fine right now and I'm seeing new growth. I'll do my partial change w/ distilled water tonight and lower the pH some more.
 

rkymtnman

Well-Known Member
Ah, ok.

They seem to be doing fine right now and I'm seeing new growth. I'll do my partial change w/ distilled water tonight and lower the pH some more.
at some point, the ppms will be low enough where you should see a slight drop daily.
 

kratosxxl

Well-Known Member
you are correct but with high ppm source water, feeding seedlings becomes harder. let's say your plants can only handle 200ppm: you have no "room" to add nutes.
maybe try RO/distilled water until the plants get bigger and can handle more nutes.

if ppm goes up, your feed is too strong. which will lead to nute burn which will lead to nute lockout and then plant death.
I think ppm strong/ weak has to do with strain and palnt health too, i top fed mimosa clones 350 ppm (water 250 ppm ) and grew amazing also i top fed 600 ppm (250 ppm water my current gelatos) 9 day old clones and they grew fine, i also use 3 stage filtered tap and ph always goes to 6.4 after 24 hr , so if you can make ur nutes in separate container let it sit for 24 hr or more then adjust ph, just make sure the room is cool so u wont get any algae etc , regarding ppm if u dont have any roots in water ppm should stay same , maybe rise just a bit due to evaporation. make sure ur ppm reader is working fine and calibrated
 
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