To find out when it’s time to harvest your plant, you can use a jeweller’s loupe or a small microscope to regularly check your plants’ trichomes. You can observe whether the trichomes turn from clear to a milky white colour. If many of the trichomes you see are still clear and transparent, it means it’s still too early for harvest. But when most of the trichomes have an amber colour and an opaque clarity, this means that the THC content of the buds is at its maximum and the plant is ready for harvest.
Keep an eye on water level!
As your plant continues to grow and ripen, it can be a very thirsty customer. We have been draining and filling the reservoir every 7 days now for weeks and you may notice that during your drains lately, not much is coming out. Keep an eye on your water levels for the last couple weeks of your grow. You can always top up after a couple days, the system will adjust the nutrient solution for you.
Is my cannabis ripe yet?
We were looking at our trichomes twice a week, let’s step that up a bit. Every other day for the next couple of weeks you can take a quick peek to see if you are at 50% cloudy, 20% amber. When you harvest is completely up to you, this is my recommendation. If you harvest a bit early, your cannabis will be a bit more up, and if you wait to harvest after more trichomes turn amber, you will have a bit more of a sedentary effect from your bud.
Decrease night temps for colour change
Several strains of cannabis in the purple family (Grand Daddy Purps, Purple Kush) will actually show the colour purple in the leaves and bud. Although most of this is accomplished through genetics, having the temperature cool at night (16 degrees celcius area) will help the purple develop. Be careful though, too low of a temperature can slow or stop growth completely. In my home during the summer, the basement is much cooler than other parts of the house. Is it worth draining, moving and refilling the Grobo to get awesome purple buds? Yeah, quite possibly. 
It’s time to groom your plant!
It’s important to keep your Grobo clean and free of leaf debris. Often over the course of your grow, leaves die, fall off, become pinched in the door and end up on the lid or ‘gasp’ in the reservoir. It is important to keep both the tank and the lid free of dead debris to help fight bugs or bacteria from gaining a foot hold. It’s much better to be pro active and avoid an issue than have it crop up and have to deal with it.