It is not a good idea to do 100% water change. The beneficial bacteria require to stay wet in order to survive. Being out of water for more than a few minutes will kill them and crash the cycle. I'd rather do several large partial water change than a single 100% water change.
Since you use RO water, what is the hardness and PH you aim for after you rebuffer it?
After you get fish, you have to be very careful to make sure you get the same number every time. Fish do not like sudden change in water hardness and PH. It can shock and kill them.
Getting stable results after 12 hours I have my RO water ready today and waiting to do a big water change for new fish today.
My water parameters after reconstitution should be
PH: 6.6-7.0
KH: 0 - 2
GH: 4 - 6
Water temp: 72 degrees fahrenheit
Otocinclus Catfish is not a good test subject. Not only their sensitivity is too high, but some of them also can't be converted into eating anything but natural algae.
Is your goal to have a complete shrimp tank with nothing in there to eat them? Is it why you don't get other fish because Otocinclus won't eat shrimps?
Yes, that's the reason why I chose to get Otocinclus because they're sensitivity is high and they're doing just fine eating my organic zucchini I'm getting high grade crystal red shrimp and Oto's are the only tank mates I would trust having with high grade shrimp.
Crystal red shrimps are another sensitive species due to generations of selective breed.
I hope you are not trying to use them as test subjects. Usually the tank will establish itself better over time even after it's already fully cycled. I would have started with hardy species, then add more sensitive ones after 3~6 months.
Much love guys couldn't do it without your help my first shrimp tank 