Plants growing too slow??

[hoff0560]

So no pics yet, but here it goes....I've got 4 plants, Big Bud from Nirvana seeds, about 6 inches tall with about 6 nodes (so not much stretching) in rockwool 6 inch cubes with a flood and drain system. My cabinet is 2'x3'x5'. I feed them twice a day with dutchmaster nutes. I've got a 600w HPS about 1.5 feet from the tops on 24 hours a day. They look great, really green leaves and thick stems, and a lot of white roots coming through the bottom. Ph is usually 5.5-6 and TDS states 1100-1475ppm. Here's the problem(?), are they growing too slow?? They are 6 weeks from seed and by looking at other posts, it seems I should be ready to flower. If these double in height during flowering they wouldn't even be 2 feet tall, and I can't imagine much yield from that.
I haven't used H2O2 yet because my nute solution is still pretty clear, but I guess there could be unseen algae growth. Could this be slowing me down???
This is my first grow so any and all comments are welcomed, Thanks.

 

[Al B. Fuct]

rockwool 6 inch cubes with a flood and drain system. My cabinet is 2'x3'x5'. I feed them twice a day

RW is highly absorbent and can't be flooded frequently. You're probably overwatering. Slow growth is a telltale, along with yellowing lower leaves. Reduce flooding to 1x/day for about 3-4 mins. Use H2O2 50% grade @ 1ml/L in your tank every 3-4 days.

 

[hoff0560]

RW is highly absorbent and can't be flooded frequently. You're probably overwatering. Slow growth is a telltale, along with yellowing lower leaves. Reduce flooding to 1x/day for about 3-4 mins. Use H2O2 50% grade @ 1ml/L in your tank every 3-4 days.

I've been watering 2x a day for 15min. So, the plants get enough nutes from only once a day feeding?? I guess that's good since it saves on nutes!!
Thankx.

 

[Al B. Fuct]

Also, pH 5.5-6 is a rather broad range. Needs to be 5.8 +/- 0.1.

Is the pH jumping around? H2O2 should fix that- pathogens can cause the fluctuation.

 

[hoff0560]

Also, pH 5.5-6 is a rather broad range. Needs to be 5.8 +/- 0.1.

Is the pH jumping around? H2O2 should fix that- pathogens can cause the fluctuation.

I thought the ph might go down and the ppm to go up just because of the evaporation, I started with 10 gallons in a resevoir and I have to add probably a gallon every 4 days. I'll definitely be trying the H2O2.....

 

[NewGrowth]

Your PPM seems really high for Big Bud at only six inches no yellowing? I agree with the once a day watering too especially at this height. Drop your flood cycle down to about 5 min too. Add that H202 now before you have problems! Di you pre-treat your rockwool not doing this will cause PH flux too.

 

[Al B. Fuct]

I've been watering 2x a day for 15min. So, the plants get enough nutes from only once a day feeding?? I guess that's good since it saves on nutes!!
Thankx.

yep, 15 mins flood is far too long.

RW has a strong wicking action, you could water for only long enough to raise the flood level 1" up the cube- and it will be saturated!

Saturating RW drives all air out of the material. Roots must have O2 to form. You can get O2 to the roots by running an airstone in the nute tank (which you should be doing anyway if you're not) and also by use of H2O2. However, if the RW is saturated, no new solution will be taken in by the cube.

Your 6" RW blocks will hold enough water to get the small plants through at least 2 days, larger more vigorous plants can be watered 1x/day. Don't water RW until about 50% of the stored water is removed by the plant.

Flooding RW more often than is needed to replace water taken out by the plant is NOT helpful. Saturated RW can't take in any more water.

 

[NewGrowth]

These are great rock wool tips! Thats why I love flood tables they are so low maintenance

 

[hoff0560]

Your PPM seems really high for Big Bud at only six inches no yellowing? I agree with the once a day watering too especially at this height. Drop your flood cycle down to about 5 min too. Add that H202 now before you have problems! Di you pre-treat your rockwool not doing this will cause PH flux too.

Ya, I pre-treated the rockwool. No yellowing, so I guess I've been lucky huh?
Only 5 min a day, shit, I've got one of those timers that only has 15 min increments. I guess it's time to buy digital.

 

[Al B. Fuct]

I thought the ph might go down and the ppm to go up just because of the evaporation, I started with 10 gallons in a resevoir and I have to add probably a gallon every 4 days. I'll definitely be trying the H2O2.....

The pH should stay pretty much constant with tank level changes, but since RW does have some limestone dust remaining from mfg, this may cause tank pH to rise slightly (+0.1 to +0.2) over a few days of that tank being used to flood the RW. After a while, all the limestone dust is either reacted with acids in the nutes or is flushed out and pH will stay closer to your 5.8 mark without any intervention.

The ppm may rise as the water level drops, but if the tank size is closely matched to the number and vigor of the plants, they may eat the nutes at the same rate they are using the water, causing ppm to stay close to the mixing day target even as the level falls. 5L of tank volume per plant is pretty close to optimal for a tank you expect to last 14 days before dumping & renewing the solution.

Try not topping the tank with plain water as the level falls and see what happens to the ppm. As long as ppm stays put and there's enough water in the tank to keep the pump submerged, there's no need to top up the tanks.

Your PPM seems really high for Big Bud at only six inches no yellowing?

I run my flowering tanks all at 1400 from go to whoa. Even clones just introduced to the flowering area are quite happy going straight to 1400 on their 1st day.

 

[Al B. Fuct]

Ya, I pre-treated the rockwool. No yellowing, so I guess I've been lucky huh?

Very. I would not be looking nute burn probs (cooked leaf margins & tips) at the strength you're using, but I WOULD be on the lookout for yellowing across the entire lower fan leaves as well as droopy leaves all over the plant caused by overwatering.

Only 5 min a day, shit, I've got one of those timers that only has 15 min increments. I guess it's time to buy digital.

Yep, gotta have a digital for the single-minute increment programming ability.

 

[hoff0560]

RW is highly absorbent and can't be flooded frequently. You're probably overwatering. Slow growth is a telltale, along with yellowing lower leaves. Reduce flooding to 1x/day for about 3-4 mins. Use H2O2 50% grade @ 1ml/L in your tank every 3-4 days.

Hey Al,
In stores all they have is hydrogen peroxide 3%. So do I need to use 17 times the volume to get to the 50% or when you said H2O2 50% did you mean half water and half hydrogen peroxide???

 

[Al B. Fuct]

Hey Al,
In stores all they have is hydrogen peroxide 3%. So do I need to use 17 times the volume to get to the 50%

If all you can get is 3%, the dosage rate is 17ml/L.

With 3%, a 125L tank requires 2125ml, every 3-4 days. 3% is thus impractical in most hydro ops.

You will not find 50% & 35% H2O2 in your local discount shop or chemist. You'll have to go to a hydro shop or perhaps a supplier of foodservice equipment. 35% is sold as 'food grade', meaning it is used for sterilising foodservice equipment.

 

[hoff0560]

If all you can get is 3%, the dosage rate is 17ml/L.

With 3%, a 125L tank requires 2125ml, every 3-4 days. 3% is thus impractical in most hydro ops.

You will not find 50% & 35% H2O2 in your local discount shop or chemist. You'll have to go to a hydro shop or perhaps a supplier of foodservice equipment. 35% is sold as 'food grade', meaning it is used for sterilising foodservice equipment.

Thankx al,
My ladies have grown 3 inches in the past week and really bushed out...Thankx again.

 

[Al B. Fuct]

great to hear it, hope it keeps on going well

 

[iloveit]

If all you can get is 3%, the dosage rate is 17ml/L.

With 3%, a 125L tank requires 2125ml, every 3-4 days. 3% is thus impractical in most hydro ops.

You will not find 50% & 35% H2O2 in your local discount shop or chemist. You'll have to go to a hydro shop or perhaps a supplier of foodservice equipment. 35% is sold as 'food grade', meaning it is used for sterilising foodservice equipment.

Sorry to barge in but I have a quick question for AL.
If Hydrogen peroxide (at 35%) is used for sterilising food service equipment does that mean I can use this to sterilise my scissors, pruner and snips when I finished trimming and cutting clones for next use of cuttings?

If not what would you recommend?

Sorry for my stupidity but Im a super noob

 

[Al B. Fuct]

Sorry to barge in but I have a quick question for AL.
If Hydrogen peroxide (at 35%) is used for sterilising food service equipment does that mean I can use this to sterilise my scissors, pruner and snips when I finished trimming and cutting clones for next use of cuttings?

If not what would you recommend?

Sorry for my stupidity but Im a super noob

Not stupid at all, good question.

H2O2 is a very good steriliser but it is a lousy solvent for oily plant resins. If you sterilise your cuttings scalpel with H2O2, you will find plant oils (kinda purplish) will build up on the blade while you are working.

If you sterilise your scalpel with alcohol (denatured alcohol aka methylated spirit, about 95% ethanol), the blade will be sterilised and oils removed at the same time, making cuts more easily & neatly.

Ethanol is superior for cleaning the thick resiny goo off your manicuring shears & fingers after manicuring, as well as removing resins from your bong.

H2O2 is better used as a steriliser for plant contact surfaces & solutions.

 

[iloveit]

Cheers Al thats just the info I needed to hear. As always Al to the rescue

 

[hoff0560]

Ethanol is superior for cleaning the thick resiny goo off your manicuring shears & fingers after manicuring, as well as removing resins from your bong.

Hey guys, just wanted to give you another option. If you ever have gummy or oily buildup that's hard to get rid of, try using some acetone (usually found in nail polish removers, but I get the pure stuff from a hospital). It works wonders. Obviously rinse well with soap and water after...Just my 2 cents.

 

[Al B. Fuct]

Sure, acetone is a good solvent for oils. If you can get it for free, great. It probably doesn't need any sort of rinse after use- acetone evaporates readily due to a rather low evaporation & boiling point. The volatility of acetone (boiling point 56C) means it is a bit more of a fire hazard than ethanol (boiling point 78C). Keep clear of pilot lights or other naked flames when using it.

However, dunno about you, but I can't stand the smell of acetone.