Plants growing too slow??

**hoff0560** · 09-01-2008, 12:53 PM

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** · 09-01-2008, 01:18 PM

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** · 09-01-2008, 01:27 PM

Originally Posted by Al B. Fuct

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** · 09-01-2008, 01:32 PM

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** · 09-01-2008, 01:36 PM

Originally Posted by 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.

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** · 09-01-2008, 01:41 PM

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** · 09-01-2008, 01:41 PM

Originally Posted by hoff0560

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** · 09-01-2008, 01:44 PM

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

**hoff0560** · 09-01-2008, 01:46 PM

Originally Posted by 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.

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** · 09-01-2008, 01:54 PM

Originally Posted by hoff0560

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.

Originally Posted by NewGrowth

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.