An Update And A Couple Of Questions

So many sections on the forum, so I wasn't sure where to post this as it should probably go in a number of them, so I thought I would use this section!

So our tank is fully cycled and thriving. We had our ammonia spike, followed by our nitrite spike, but as we were both on leave for a couple of weeks after Christmas, we were able to keep on top of it with water changes and daily testing using the all-seeing,  all-dancing API kit.

We are now consistently at the following parameters; 8 / 8.2 ph (difficult to be totally sure), 0 ammonia, 0 nitrite, 5 nitrate. We have a lot of plants in the tank, which are growing and rooting rapidly. I'm sure I can almost see some of them grow before my eyes!

We are lightly stocked from our LFS with Harlequins, Schwartzi corys and Bosemani Rainbows and will not be adding anything else for a good while to ensure everything continues well - very hard given how amazing our LFS is. However this is a longterm project and has been a wish for many years so it's worth taking our time. We bought a big tank, in the knowledge that if we didn't we would want to upgrade quickly, which would not make financial sense, so are the proud owners of a Juwel Rio 240 in white, with a venturi, and I love it. It's certainly a talking point. I also picked up a second hand Juwel Rekord 600 tank and cabinet in brilliant condition and at a super price, as a quarantine tank.

As @Sue knows, I am also keen to keep shrimp, as I am fascinated by them, and this was a definite from the start. Ideally i would like to keep them in the main tank as a further point of interest, however, I know they are sensitive to many medications. I need to know if they are suitable with the fish we currently have (I think the rainbows are my main concern), whether to go for amano shrimp,  cherries, or a combination, and most importantly how long should I leave the tank before I look at adding them. Also, should they be quarantined before adding to the main tank? We are going to be keeping a sponge in the main tanks filter for when we need it, and would also use water from that tank so that it woukd be cycled immeduatly if we needed to use it. I have the right substrate for them, plants, roots and bogwood, with further plants to be added  (also aware of making sure the plants are shrimp safe / quarantined. 

The alternative of course is to turn the quarantine tank into a shrimpery and keep an eye out for another quarantine tank!

I've attached a photo of how our tank looks at the moment. It's not the best photo, but it's just to give an idea.

Sorry for the long ramble ... I promise to try to be more concise in the future ...

Thanks @Sue for replying so quickly and with so much info  . I think my husband is resigned to the fact that the Rekord is likely to become a shrimp tank but initially I have to pretend that that was never my intention 

If I were to initially try adult amanos in the big tank, how long do I have to leave it before its mature enough? I know that they don't add any bioload so there's no worry there.  My rainbows are juveniles so that will probably give me enough time to look for another QT   

ETA: yes we have very hard water here