Meyer lemon from seed comes up completely yellow?

The layer of clay pebbles actually impedes drainage as it raises the perched water table in the container. (See Myth: Container drainage.) Depending on their size I would consider using the pebbles as a component in a soil mixture. There would be no need for the hose if the medium itself was porous enough to allow the water to drain quickly. A medium can be porous and yet moisture retentive.

 

*off to remove the hydrokorrels*
I guess the impeding explains why no water came out of the bottom? If it drains through nicely without the clay pebbles (not very small) I'll take the hose out too.

Will save the hydrokorrels so I can mix them through the soil for when I get a mandarin tree and have to repot that.

 

Tree now in all soil with no hose and some decorative clay pebbles on top (read: I'm too lazy to fish them out by hand and it won't harm the tree).
And it makes sense - nature doesn't have a hydrokorrel layer at 1 m deep either. And water travels best through 'same consistency' material and will see any difference as an obstacle.
But since I'm new to this and Google had hydrokorrels all over the place, I thought I'd better go with the majority advice.

Going through the Myth website I also came across an article that said there are quite a few plant species where the new/young leaves are red. So that eliminates a point on my to-do list: google and see if jasminoid red leaves means the plant is in trouble. Since there was a lot of new growth I figured it was normal and the plant was happy, so it was pretty low on the to do-list, but now it's off ;)

 

Many citrus growers add bark nuggets and perlite to the mix to make it more porous. Calcined clay chips such as Turface is another option; it may be of the same material as hydrokorrels but in a gritty form.