Adding Otos?

[Laura Noob]

Hi all.
I have an established 64l tank (inhabitants listed in signature below). I live in a moderately hard water area with pH 7.8 but am totally in love with Otocinclus catfish and have always wanted to have some in my tank! I know they’re happiest in schools of 6 or so and, if I can, would be looking to add this many over time. My levels are all stable at ammonia 0ppm, nitrates 0ppm and nitrate 5ppm. I have 2 questions:
1) will the otos be ok with the pH and hardness of the water?
2) is this going to overstock the tank and put everyone else at risk?
I have considered doing partial RO water changes but I am not so sure that the other inhabitants would take too kindly to the drop in mineral levels - particularly the Guppies and shrimp.
Thanks in advance for any advice.

[TropicalFishForums]

[plankton]

How hard is the water? 7.8ph sounds as though it may be very hard, unless you live in Scotland where it'll still be quite soft.
My water is 7.9 dGH and they do ok, my ph is only 7.0 though. I wouldn't try with anything harder than 8.
They are mainly wild-caught so need soft water as they don't adapt easily.

[Stephen]

Bournemouth water is hard at 15dGH so not ideal for Oto.