Gravel Pans or Trays
 

I always seem to get bugs when I purposely add water to my gravel trays?

Do you guys add bleach or some other disinfectant to keep that water from getting stagnant?

What kind of "bugs"? Pill buts or sow bugs? Other?

Rather than look at the bugs in the gravel tray, I would look to the mix in your plants as I suspect the bugs are coming from broken down mix in one or more of your plants. The bugs are just looking for moisture.

CL

I would tend to agree with CL. However, something that I have heard of a few people doing in their humidity trays is to fill them with a dilute bleach solution (I think it was something on the order of 1:10 dilution of bleach to water). I think there was also another post here on OB that describes using this bleach solutions as a fungicide/algaecide when watering your orchids. **However, I am not 100% sure on that** But, if you use that solution in your trays purely for the humidity factor and you don't have any of your plants sitting in the water, I don't see why it would have any negative effects- should be effective in cleaning out those bugs.

I think they are fungus gnats. They look like fruit flies. All of my orchids have been repotted in the last month or two and I thoroughly removed the old media. There are some other house plants in my sunroom. So it's possible that they live in the dirt of the dracenas and then swarm to the sitting water. Either way I don't want them depositing eggs in the orchids.

I was given great advice by another member of this board, rather than using bleach, which can be malodorous, use Physan. I have tried this in all of my humidity trays and it works. Plus if it gets in the plant, it won't suffer bleach burn.

Use a little bit of mosquito dunk in the water or get a butterwort and the fungus gnats should disappear.
I have a few plants that need to always be wet and that need organic fertilizer. These conditions just breed fungus gnats. Fortunately, the only way I know that I still have fungus gnats is that I see them on the leaves of my butterworts. If you don't have one of those amazing plants, they are a great addition.

I haven't had that problem, but I have a LOT of evaporation going on in those humidity trays, which IMO, is what you want when you use one!

My thoughts? More pebbles or less water or a combination thereof. The increased surface area for the water to contact with when you add more pebbles should give you more evaporation and better humidity around the plants and the water should evaporate completely in about 24-48 hours, so you should have to refill them with fresh water every day or so. If it's taking longer than that, you're not getting enough evaporation to raise the humidity around your plant.

I've been using the Mosquito Dunks to successfully control fungus gnats. I put a few bigger chunks in the gravel/drip tray and I'll occasionally sprinkle some finer bits on the media of a potted plant after watering if I notice gnats on the plant. It wont kill the adults but it will kill the larvae and soon the population will decline.