The best thing is to use a special plant food for orchids. You can buy them in plant shops. It says on the label how to use it, or better, how much to add. It's good to it how it says on the label otherwise you might overfeed your orchids. If you feed to much, your orchids might get a damage which can kill your plant.It burns the roots and you might notice it too late. I use calc free water. I either use filtered rainwater or when I have not enoug, I use filtered water which I also use for the coffe machine.

I feed most of my orchids from spring to autumn. I feed them every second week. Some cultivators feed only every 3 weeks. Start with feeding as soon you see that the orchids start to grow in spring.

Mix every time a new pot with feeding water. It's not good to keep the rest from last time. You also should use the plant food only for one season otherwise it's possible that the chemical composition changes.

Beginners can use the normal plant food for orchis. It contains what they need. Advanced ones feed their orchids depending on its needs.Food with a lot of nitrate is good for the growth . After this they continue with food with phosphate , good to bild flowers.

One thing is important: Don't feed your orchids when they are in the resting period. There are orchids which need an absolut resting period. As soon as it start to grow, bild new roots then you can start to feed.

You only should feed healthy plants. Don't feed plants with damaged roots. They can't use the nutriation. First give care to your orchid that it can build new roots. You might give a bit food over the leaves. Put a bit from the water with the plant food in a sprayer and spray the leaves. Mounted orchids you either dive in water with plant food or you spray them. New potted orchids, parts of orchids and baby orchids, don't feed until they developped enough roots.