coconut coir, gnats.. general help please...

Hi all,
Hope everyone is well....

A couple of questions i have if anyone could be so kind to help regarding a grow ive just started...(indoor).. (250w hps.. 90x90cm grow space.. 1.8m height tent);;; dimmable ballast turned down to 190w for the vegging stage... and will turn up to 250 once in flower...

3 weeks ago Iplanted 2 seeds anfer germinating them in water for a few days until they cracked open.... ( dutch kush and also deliciuos candy) both femanised...

I have planted them in some coconut coir.. ( the stuff you add water too to make it expand).. But have not added any perlite to it..... they are 3 weeks in and about 3inces high now with about 4 sets of leaves on them.. ( sry no pics)....


QUESTION... the size of the pots are 10l..... is this big enuff to grow them from seed to weed?

QUESTION.. can i grow them entirely in the coconut coir onlly ( i have not added perlite to them)

QUESTION.. is the 190w sufficient for the vegging stage during the 18/6 cycle.. and then ok to flip onto 250w once flowering.. ( a bit worried about heat issues while still small)


QUESTION.. i have read that the coconut coir can cause fungus gnats... annd am worried that i may get them.... is it a guarantee i will using this coconut coir... and if i did is there either a way to easily get rid of them... or would it be advisable to repot them into a compost/perlite mix.... without too much stress

QUESTION..i have made a scrog screen for them as plan to train them down to increase yield.. ( first time trying this method).. screen i... and its 10 incehs above the height of the pots i am using.... is this tall enough for a scrog.

A lot of questions i know.... bit of a newbie to this.... have tried a few grows in the past.. have always listened to bad advice from people and have ended up frazzling plants.. over watering.. etc etc.. lol.... so want to get this one spot on...with some advice from you experts....

Any help would greatly be appreciated..

Yes but that's a smallish pot. Are they fabric or plastic? If plastic I'd definitely pot up or over to fabric, root bound issues seem less common.
Yes, no perlite needed.
Yep, plenty of veg light.
Fungus gnats are attracted to decayed and decaying plant matter, so if you're using anything organic, you could get fungus gnats.
I've never scrogged, no idea sorry.

In coco it seems impossible to overwater, but I've only done it, I've never really read up on it. I had to water daily.

Thank you for reply matey....

So I should turn the lights to the full 250w even while vegging?

And use some bigger pots?.... As height is a bit of an issue... Would wider pots be ok.. As opposed to taller ones?..(pots are plastic by the way).. Didn't know if it would stress them if I repotted them... Should i wait a little longer for the roots to get stronger before doing it... Or is it better to do sooner rather than later.

I would. And if I had the space and ventilation I'd put both lights on.

Wider is good.

I wait till I see roots growing from drainage holes, or just by look.

Provided you transplant in veg and give it a few more weeks before flower, transplants are easy and generally beneficial.

I may I have wrote that wrong... I only have the one light in the room.. It's a 250w ballast.. But has different settings on it.. 150w.. 190w.. 250w.. And a super lumens.. 290w mode.... I've now flicked it onto 250w...

The height of my scrog screen I have made in accordance to the current pots... They are 10" high And are 10" wide..pots.. Not 10l if that makes any difference?

How long in total should you give it in veg?. Obviously with scrogging u need to fill up a bit of the screen... But going on the current rate they are growing... I would anticipate.. Easy another 4-6 weeks in veg to give them chance to fill the screen..... Is this too long to veg mate?

You can't veg too long, really, but I believe anything past 6 months is basically pointless.

Not sure if SCROG has to account for transition stretch but I'd say it's ready for the flip when the screen is full.

Excellent advice buddy... Really appreciate it....

Won't be vegging for anywhere near 6 months that is for sure!

Will have a look at raising the screen tommoro.. To allow for repotting into some bigger pots....

I'll try and get some pics up at some point or atleast the final outcome of it...

Thanks again for your help and quick replys.

Mosquito Dunks crumbled in soil and water will keep gnats from reproducing. Part of every mix.

What are mosquito dunks?

Never mind I've had a look now and have seen what they are..... But seem a little expensive....

Is there any other option to treat the coconut coir......

Or would it be easier when I repot the little ones to just switch to a compost/perlite mix.... As I've never heard of these gnats when using this

Gnats can be in anything castings, mulch, name brand mix, peat.whatever. Google mosquito dunks. Get those or something higher priced from a grow shop. They contain bacteria that feed on the larvae. Not expensive and I'm a couple weeks they are gone. I also sprinkle DE on top of soil and around the tents. Neem seems to help also.

I can't imagine you'll have gnat issues in coco. I've never heard that. Gnats like moist, decaying organic matter to lay eggs in, at the first couple inches of medium. Coco just isn't usually ideal.

I've done coco indoors and out with both synthetic and organic nutrients and haven't had them in my coco plants.

Coco is not magic. If you have 'em, you have 'em. Gnats transplant easier than your plants. See ya.

Thanks again for the help everyone.... Think I'll just pot into bigger pots.. And take my chances with the coco... And just get some stuff as suggested for them just in case...


One more question.......

My setup is plugged into a 4 way extension lead... That's I turn on and off manually 18/6.... Running thru the nite to help with temp......

I'm due to start work in the next week or 2.. So will not be home during the day when the lights need to be off......

Can i plug a timer into the 4 way extension to timer the lights on and off.... (guessing it won't be a problem to leave the fans/filter/air intake running for a bit of circulation and air flow etc....

But is it safe to use a timer for the lights in this way.. Or should I just timer the lights separately in a mains timer.

Thanks again.

Hi !
I had a gnat problem once that gave me a 50% yield than i usually get. Got so bad to the point that all my leaves started to yellow and grey out. I think all my roots were dying.
Anyway, for the next grow, I literally spent 30m-1hour in the grow room every day with a can of fly spray. I think i ended up using 4-5 cans. No matter how many i killed. They always came back. By chopping time there was 10,000's of dead gnats on the floor. I used airpots which may have accelerated the problem.


I'm using fine mesh nets over my pots now and have not seen a single gnat/fly since!