When to add more shrimp?

[shrimpstudent]

Hi everyone! I am pretty new to the shrimp world (but have experience with aquariums), as a few weeks ago I was spontaneously gifted an Ecosphere with five opae ula. I immediately began researching and preparing a new 1-gallon tank for them, and moved them into it about a week ago. I am extremely happy that they have all been doing great so far! However, I know that the 1-gallon tank is a bit large for just five shrimp, so I would like to add some more and also maybe a snail. How long should I wait to add more shrimp? I've read other posts on here saying ~20 as minimum for a 1-gallon, so should I add ~15 all at once or buy them more gradually? Are the shrimp I already have vulnerable to disease/etc from introducing new shrimp? I know they are "supershrimp" but I don't want to jeopardize them.

My apologies if these are pretty obvious questions, but considering the spontaneity of my new ownership of them and the fact that I am a college student in the middle of finals season, I haven't been able to do as much research yet as I would have wanted to.

Thanks!

[Super Jess]

Their bioload is so tiny that adding 15 to your tank at once shouldn't be a problem. Order your snails at the same time!

[shrimpstudent]

Thanks! I was mainly wondering though when I should add them in general, considering I added the current ones a little over a week ago?

[i<3Opae]

Anytime really. You could add them as long as the current ones are faring well.