Is my extractor fan giving lower yeilds?

Hi Guys,

Im nearly at the harvest stage of my 1st grow and my yeild is look..well....poor.

I think that maybe a lack of co2 could be the cause.

My room is 80cmx80cmx160cm using a 4" RVK fan.

I think the fan maybe too powerful as the walls of the tent are slightly sucked in all the time, maybe the fan is sucking out too much and not allowing any co2 buildup? The walls of the tent should not look like someone who has just sucked a lemon should they?

Do you think this could have a detremental effect on yeild guys? Have any of you experienced this before and is the fix simply a new (smaller) fan?


Any advice is greatly recieved

do you have an intake to supplement fresh air/co2??

negative pressure is better then posotive IMO cuz you know air/HEAT is being exhausted

is your room completely sealed?? otherwise air is coming in through the cracks...

Thats not the problem. you want your fan to completely exchange the air in the room 4-5 times a minute approx.

well iam going in a closet, with a boxfan moving air to control heat. nothing really making sure how much air is being moved, but it aint much. the fresh air it gets is merely from the bedroom, which gets its air from the living room via a swamp cooler pushing in from the ceiling. the ventilation is less than ideal, but my yields look fine for the plants size, i would reccomend looking at other factors if you yield is suffering, because it sounds like you have more than enough fresh air to sustain the plants.

Ah...right, well thanks for the replys guys......ido have intake for fresh air, and if it needs to be replaced 4-5 times a min then im sure my fans does that. Also, yes its completly sealed, that was my first thought.

But i want to get those giant colas that isee people growing, massive plants with huge yields. Im sure this come from experience but i have no idea where i went wrong. Maybe i didnt water enough? I was wating 3-4 days as a means of toughening them up so they dont become dependent on watering. I was growing in soil, but didnt start nutes until 3rd week of flowering (after vegging for 5 weeks)

Do you guys think that may contribute? Maybe the fact im using a 250mh bulb for flowering? I have 5 plants, maybe they need a higher wattage?

250mh may be a bit low for 5 plants, but i havnt made the jump to anything HID yet so i dont actually have any experience to share. i would say it probably comes down to a few factors:
1.Genetics. this is the single most important part of your grow concerning yield. did your seeds (or clones) come from bagseed or dispensary or mailorder seeds?
2. Nutes. you want to really dial in the nute schedule, and it will vary on the strain. sometimes you get lucky and find its sweet spot all the way through (as i did with the plant in my avatar, which is bagseed), other times people will try multiple times before they find out what their strain likes.
3.Lights. again, iam not expert, maybe someone else can help here, but sufficient light is key. how many lumens does that 250mh put out? the sun puts out 10k lumens per sq/ft, i personally only aim for about 5k (per sq/ft) in my closet.
4. Temps and pH. Both of these factors are often overlooked, but can be very important when it comes to how quickly your plant grows, thus, how many flowers your plants may put out.

these are just a few thoughts off the top of my head. i wouldnt take anything i say as if i were an expert, iam not. i am merely regurgitating information that i have learned throughout my 1.5 grows =D

Klosetking, I appreciate your thoughts. To answer, 1. Seeds came from Big Budda (Cheese), all germinated fine (apart from i think they stretched a little during propagation...error 1!). 2. Nute wise, i fully admit i was slow on the uptake, and being my first grow i didnt want too much hassle, big i went for the standard BioBizz range using All mIx soil. I have hit so many issues from start to finish what with over watering, nute deficencies, having one plant too close to the light (and it pretty much caught fire!), but hey, its only a mistake if you dont learn from it right? Temp wise, i have been struggeling. I dont know where your based, but im in the UK and we have had some heat here latley, and the grow room average temp is 30+ all day. I have introduced more ventilation into the back bedroom which has lowerd the ambient temp but still in high 20c. Watering wise, only using bottled water from the supermarket from start to finish.

This leads me to point 3. And i think the penny has dropped. The 250w MH is wrong. I work in a big building in the city and my mate who works in the maintaince dept gave me a MH bulb that is used in our atrium. I was dubious when i saw it as it was a frosted bulb but funds were short and i had to use it short term (which turned long term). God knows what lumens its pumping out, maybe not many giving its frosty?

So , my next grow is 9 Super Silver Haze using those Air-pot things. I want that one to go better( obviously), thus seems i had better use a more specific bulb.

Question tho KlosetKing, what wattage do you use? and also...thanks for the pointers

anytime i hope my limited experience can help in some way =D

i personally use a 325W T5HO setup due to lack of funds to get a real flower bulb myself. 4ft 6bulb ballast. for my 3 plants, i would bet they receive an actual 20k lumens or so due to distance, penetration and light loss (which is common for fluoros) even though the total expected output is supposed to be around 30k lumens. what i would recommend is finding a label possibly somewhere on the base of the bulb, maybe find a model number or something to identify it with, then google it. again this is only if possible. it could just be an improper mh bulb.

as for temps i hear ya, i have to deal with heat myself, even with the cooler fluoros (which is partly why i settled on them for now). sounds like with your heat and nute issues we have similar problems. for now i would try to figure out your lighting is, maybe try to rule that one out. your water is probably fine, and depending on your soil your ph should be fine with it. i watch my plants alot, so i usually wait til i see signs of wanting the water rather than actually figuring out a schedule (temps can vary, so the time it takes to dry can vary as well).

dunno if this one helped as much, but best of luck

ya you need a clear bulb not a coated bulb..thats y ure not producing buds IMO!!!!!! MH will give you more airy buds then dense but in return will give you more higher thc content or thats what research has shown.

seanec327 said:

ya you need a clear bulb not a coated bulb..thats y ure not producing buds IMO!!!!!! MH will give you more airy buds then dense but in return will give you more higher thc content or thats what research has shown.

Click to expand...

That is kind of true, mh has more ultraviolet light in it that breaks down thc, and we all know what happens when you breaK something down in nature usually....it comes back stronger than ever. You can get a uv light to use in conjuction with an hps or use one of each or, ive never tried it but i keep hearing good things about it, a ceramic metal halide.

Can't be a pornstar overnight!