how long I can use a diluted fertilizer? Algae fertilizer any good?

[lobotomizedgoat]

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.