Shrimp doing very well am pleased to say. The PH crashes were sorted shortly after I got the marine buffer, but for all that I'd highly recommend it for emergencies and the shrimp certainly didnt mind it in their tank)
On yet another salvo to my LFS for more RO, when I told them I was tearing my hair out with these PH crashes, the guy there told me I needed their added minerals (its one scoop per 25ltr) and this totally did the trick - my PH has been stable at 8 from there on in, but like I say, the Seachem is well handy (albiet a bit pricey) for any PH plunges whilst you sort out the culprit at least!
Tank is now cycling properly. We had a ammonia of over .25 then Nitrite of 1.00 a few days later - have now got my backup plastic tank of RO (the cheapo heater I got with the tank but sidelined has come into its own now, as I can do water changes with next to no hardship to the shrimp with heated clean water)
Lastly, I treated them to a Fluval prism and this they really like as its got all diff colours that can be subdued greatly and the green/moonlight blue on very low must be simulate quite well their native pond habitat? they are all moulting well and feeding on the shrimplab algae & spirulina for treat (I cut tiny bits off algae flake to feed as I only have my few Opaes )
Am SO proud of these little shrimp! :)