Is RO water okay to use in tropical freshwater tank?

[Fishless cycle]

I posted earlier today about my tap water having a nitrate of around 20-40. When I tested my tank water it was really high so pretty concerned about it.

Should I do water changes with RO to bring the nitrate down? Also how can I do this without messing up my ph levels?

 

[Mumma.of.two]

You can safely do 50/50 without having to add any additives. Start off my doing 1:4 RO:tap and work your way up to 50/50.

 

[Fishless cycle]

You can safely do 50:50 without having to add any additives.

Thanks for this. I'm thinking about doing this tomorrow first thing and then looking into the plants you suggested, in my other thread today, more longer term.

Hopefully this will bring my nitrate level down fairly quickly. Do I need to treat the RO as I would tap water?

You have been a fantastic help so thank you

 

[Mumma.of.two]

No RO doesn't need treating. When I said 1:4 that was for the water replaced during a water change. Not for the whole tank straight off btw. Thought if make that clearer.

No problem

 

[Fishless cycle]

No RO doesn't need treating. When I said 1:4 that was for the water replaced during a water change. Not for the whole tank straight off btw. Thought if make that clearer.

No problem

Ahh thank you. I was thinking get a bucket and fill half water and half RO. I misread. Okay that's great I'll start with just 25% RO untreated.

 

[Amicus]

Do you have live plants and/or any shrimp?

 

[Amicus]

I asked because RO water is all but stripped of trace elements and even fish need them. If you plan on getting shrimp or have live plants you might have to dose certain elements for them and that can be a pain. Nitrates at 20-40 ppm isn't bad, I am from the school of thought that if your nitrates are holding at 20-40 then your bacterial colonies are stable, working and waste is being processed efficiently. You don't want nitrAtes at zero.

 

[Mumma.of.two]

I agree that 20-40ppm isn't bad but the OPs tap water starts at 20-40ppm. So it's that plus the nitrate produced by the bacterial colony. Cutting the tap water with RO will soften it, reduce the pH and reduce the amount of nitrate going into the tank. There should still be enough minerals with half/half IMO.
By introducing the RO slowly the OP should be able to gauge how everything is reacting to the change in water chemistry.

 

[Amicus]

I agree that 20-40ppm isn't bad but the OPs tap water starts at 20-40ppm. So it's that plus the nitrate produced by the bacterial colony. Cutting the tap water with RO will soften it, reduce the pH and reduce the amount of nitrate going into the tank. There should still be enough minerals with half/half IMO.
By introducing the RO slowly the OP should be able to gauge how everything is reacting to the change in water chemistry.

Spot on.

 

[Fishless cycle]

Do you have live plants and/or any shrimp?

I have three very small plants but mostly plastic and no shrimp.

 

[Fishless cycle]

I've just tested the lfs RO and the nitrate is around 10ppm and ph is 6.4 - the tanks ph is 8.2

In this area the ph is quite high and the lfs said they would be used to the high ph. It will obviously drop when I add 25% RO today. Will that be okay for the fish I have in my two freshwater tropical tanks?

22litre
5 bumblebee gobies
3 live plants

180litre
6 harlequin rasbora
8 neon tetra
6 dwarf neon rainbow fish
1 male guppy

 

[Fishless cycle]

I have now done a WC with RO water (20%) from the lfs - the nitrate is now below 40ppm... so so happy - I can breathe again

All fish are zipping about and seem happy enough.

The ph level hasn't changed much so that's good.

Thanks everyone for your help ?