Worth Using RO Water For Freshwater?

What does your water company say about your GH? That will be what they have under the heading hardness on their website.

Looking at your list, for hardness -
Bolivians can go up to 179ppm
Peppered cories to 214
Cpd and sterbais up to 268
Wcmm to 357
Crystal reds between 71 and 107. These shrimps need it soft.

And pH
Crystal reds 6.2 to 6.8
Peppered cories 6.0 to 7.0
cpd 6.5 to 7.5
bolivian rams 6.0 to 7.5
sterbai cories 7.0 to 7.6
wcmm 6.0 to 8.5


It looks like your water is too hard for bolivian rams and far too hard for the crystal reds. Depending just how hard it is, it might be OK for the rest.
The pH is fine for all except the shrimps and peppered cories.

If you really want bolivians, and to keep the shrimps alive, you do need to soften your water with RO.

As for how much to mix, that depends on just how high the GH actually is. If it is 17 german deg, you need 1 part tap and 2 parts RO for the shrimps. If it is as high as 20 deg, you would need 1 part tap and 3 parts RO.

For GH you can use german degrees or ppm (which is the same as mg/l). I use the website Seriously Fish for fish profiles as they have more species than here, and they sometimes use one, sometimes the other. It is useful to know what your water is in both units.

11 German deg would be fine for all the fish but not the shrimps I'm afraid.




You could always get a small tank just for the shrimps and use a bigger dilution.............

If you could get it down to around 8 that should be fine for the fish and plants while not too high for the shrimps. But if you find the crystal reds don't do well, you could think about one of the colours of cherry shrimp, they would be fine in harder water than crystals. And they come in several colours though you should keep just one or they'll interbreed and you'll end up with just brown shrimp.

I would err on the side of caution and take things slowly. Try using 2 parts tap to 1 part RO to start with. After a few water changes, the tank water will be all that ratio and the GH will stabilise. Then increase to 50:50 tap:RO for a few water changes till the GH stabilises again. Then to 1 part tap to 2 parts RO till the GH stabilses. Carry on like this till the tank has the GH you want. If you overshoot, do a few water changes with a bigger proportion of tap for a few times.