I would like to pre measure my 3 x weekly doses of NPK , is there any detriment to combining the three salts in containers(pre mixing each dose dry& storing it in a container).
Regards

No that's fine, the only bad mix are Fe and PO4 chemicals.

Regards,
Tom Barr

If you mean premix the dry salts and store them dry, to be dosed dry, that can be a problem if you aren't able to mix them well. It would be about 4 parts KNO3 and 1 part KH2PO4, but unless well mixed, and unless the particle sizes were about the same, the mixture might not be homogeneous.

To clarify, i want to mix my weeks dose for each of the 3 days ( Mon, Wed. Fri - 1/2 tsp. KNO3+3/16 tsp. KH2PO4+ 1/4 tsp. K2SO4 combined in 1 container,so i would have 3 containers with the NPK for each of the 3 days) this would make it easier fo just dose 1 container in the morning before i leave for work instead of measuring each salt .
Regards

That will work perfect.

If you ever leave for a vacation and plan on having someone stop by the feed the fish, set that up for the food and for the ferts.

Easy.

Regards,
Tom Barr

Thanks Tom.
Regards