Ghost shrimp are not terribly hard on the bio-load. I am not certain about snails, but I am guessing they are not big ammonia producers either. In my opinion you really should have gone fishless for a grow out tank.
So, now you have them, no turning back, right? So yes to water changes and using conditioner. A couple of key points: Make sure the conditioner you use is appropriate for your municipal water system. If it has chlorine, any basic dechlorinator will work. If it has chlorine
and chloramines then you need to use a product that eliminates chlorine
and ammonia. Please note that some water conditioners will say they "neutralize" chlorine and chloramines, but please be cautious as most times those remove the chlorine component of chloramines and leave the toxic ammonia in your tank. I know my water has chloramines. I have used both Amquel and Prime and rather like Prime. I did a test with Aqua-Safe, from Tetra, and it left ammonia in the test water, while the control water with Prime had much lower levels of ammonia.
As to how you accomplish water changes: I use a product called a Python. It removes water from my tank as it vacuums the substrate. After that, I turn a knob and it refills my tank. As it is refiling, I add the Prime to get rid of the chlorine and ammonia. Also, there are times when I want just a little tank water in a five gallon bucket, so I use a gallon pitcher (please note this is a pitcher I use only for tank purposes so it is only rinsed in dechlorinated water with no soaps) for that purpose. In this water, I will rinse out my filter media and shake off any nasty stuff (usually plant debris in my case) and then add the media back to the filter.
One last thing; if you do not already have testing kits for ammonia, nitrites, nitrates and possibly pH, you are going to need them. I suggest just ordering a Master Test Kit online from
Big Al's as it is much cheaper than buying all of the tests separately. These tests will help you monitor your cycle as it progresses and keep track of general water quality once your tank is up and running. With regular testing you can avoid disastrous spikes of toxins that occur in tanks normally.
I hope this helps and good luck with the fry tank!
PS: One last thought, what were you going to do with the ghost shrimp once you added the fry to this tank? I have ghost shrimp and can tell you from first hand experience, they love to catch and eat fry.