I dislike measuring non-liquids by volume so I use a jewelry scale to measure my fertilizer, they're only $10-15. I mix it at full strength (20-10-20) then dilute for watering.

I recently noticed some dark sediment floating toward the bottom of the container I store it in. The container hadn't been washed for a while and it was only a week since I had last filled it. A couple plants got watered with it but it they don't appear to have taken any harm. I threw it out and in the future I'm going to rinse thoroughly every time I refill, and wash with soap every few. Also, while I doubt it was a factor, I had mixed it to double strength that time.

If you mixed double strength, it is possible that you exceeded the solubility of some component(s) in the concentrate. If you are using a fertilizer that includes calcium and magnesium, you particularly can reach a point where something precipitates. If you go back to your usual mix for the concentrate, you will probably fix the problem.

Hmm, perhaps I'll get the mason jars out and do an experiment.

There’s another, easy remedy to that - mix up a concentrated solution, then dispense that to make your final applied solution.

https://firstrays.com/wp-content/upl..._Dispenser.png

Complete instructions

That's actually what I'm doing now! I guess my post wasn't very specific. Thanks!

I bought today a Miracle Gro Indoor Plant Food 1-1-1.

It says to mix 4 pumps per 1 liter of water. Is it ok or I'm better to use 2 pumps?

Is it ok to use weekly?

Expensive way to buy plant food... you are mostly buying water. No idea what a "pump" dispenses. But orchids are light feeders... I usually suggest using half of whatever it says on the bottle. So maybe 2 "pumps". If you under-fertilize an orchid, it may just grow a little more slowly. If you over-fertilize it you can damage it. So go to the low side, fertilize once a week, and observe it. It will take some months before you can tell if it needs more so be patient.

My recommendation would be to apply about 100 ppm N weekly. 1% is 10000 ppm, so you want to dilute that 100x, meaning you add 10ml/L.