CRS or Tiger Shrimp?

[Zmuda]

I'm kinda need help deciding on what ones to get? I was leaning towards Tigers as seeing as these will be some of my first shrimp.. I have 2 tanks towards shrimp at the moment. And I'm getting in a shipment of some Fire Reds so I'm looking for something that will not interbreed with them.

I have a 20 gallon and a 10 gallon.

Just did a test on the water. (Ran out of amquel+ bout 2 weeks ago so these haven't been treated since) Whats better? amquel+ or Prime?

Temp- 73 (20 gallon, trying to get to about 76), 72 (10 gallon)
Nitrate- 20ppm
Nitrite- 0ppm
Hardness(Gh)- 25ppm
Chlorine- 0ppm
Alkalinity(Kh)- 300ppm
pH- in between 7.8ppm-8.4ppm thinking about 8.0?
Ammonia- .25ppm


Anyways... What do you guys and gals think about this??? I feel pretty confident in my fish/shrimp keeping skills. Any good way to lower my pH without a R/O system? And any other tips on changing anything?

Thanks for any help.
Tom