Mixing RO water with tap water.

[vendetta]

Hi to all!

Recently I bought a RO filter for my discus tank. In the past I used to do my water changes with bottled water prepared with Acid and Alkaline buffer by Seachem in a pH of 6.4.

I recently moved to a new city where buy bottle water is very difficult.

I finished the cycling a month ago, and I added some little corydoras and mesonautas. This monday I added the first discus.

I read that RO water need to be mixed with some minerals or with tap water. I started with water changes using straight RO water.. why?.. because I needed to modify the pH slowly.

I found this post -> http://forum.simplydiscus.com/showthread.php?25733-DO-NOT-USE-STRAIGHT-RO-WATER!! where a guy recommend ask for the correct mix, because it depends of the tap water parameters.

So....

The tap water parameters are:

pH: 8.0
KH: 11
GH: 11

and the RO water is:

pH: 5.0
KH: 1
GH: 4

What quantities do you think I need to use to get a good pH for discus? (for example 6.4).

Regards.

[Second Hand Pat]

I would experiment with different ratios in a small container and measure ph as you age the water. Why are you targeting such a low ph? Breeding?

[vendetta]

Breeding is one of my short time objectives... but actually I manage pH 6.4 value since I have had discus with good results.

In the other hand I think 8.0 of tap water is very high and 5 of straight RO is very low. I don't know.. I have been read a lot of opinions related with the pH steadiness vs low pH.

What do you think?.. Do you have any recommendation or advice to give me?

Thanks a lot ;)

[Second Hand Pat]

If you have domestics I would try them in plain tap water.

[timmy82]

Yep try and stick to tap water, you may need to age it and the PH may drop if so you will need to continue using aged water. Even try filrtering the tap water and you may keep more stable steady results. I would leave the Ro until you are set up to breed them and work out a ratio with a conductivity metre.

[vendetta]

Hi!

Yesterday I did a lot of mixtures for discover which is the best percentages of RO and tap water.

The results was weird... I started with 50/50 (RO/tap).. 60/40... 70/30... 80/20... 90/10 ... and all of these with pH 7. Then with 95/5 I got pH 6.5 and with 97.5/2.5 a pH 6.

So.. I think it's strange, most part of people use something like 50/50 or 80/20... but to get a pH 6 I need 97.5% of RO water and 2.5% of tap water..

Is it normal?..

I'm starting to think that RO water is more complicated that pH buffers.. pffff...

[Second Hand Pat]

I do not really know as I have only worked with my own water. I think the makeup of the water has a lot of do with how RO and tap mix together and why I suggested experimentation. Sounds like yours may have a high KH or lots of buffering.

I take it that going with full tap is not an option? You could re-min your RO and call it a day.

[bs6749]

The tap water parameters are:

pH: 8.0
KH: 11
GH: 11


This is why you are getting the results that you find to be weird. You have a good deal of carbonate hardness in your water which acts to buffer the pH from swinging wildly in one direction or the other. Once this buffer is "consumed" or "used up" so to speak in neutralizing these acids (from your lower pH R.O. water), subtle additions of R.O. water will have a greater impact on lowering the pH. This is why you can do a 50/50, 75/25, or even a 90/10 mix and not notice much change. As you see though, once you got to a certain point (the point where the buffer was no longer capable of working it's magic on any additional acid) a 2.5% increase in R.O. water made your water 5 times more acidic!

[vendetta]

Second Hand Pat: I don't know if I can use full tap water. I moved from Mexico City to Aguascalientes City; in Mexico City I use to prepare tap water with acid buffer and acid regulator by Seachem.. and that was really fine.. mixing a little spoon of each one per 20L I got 6.4, always.

But know.. the water is very different; my discus (I have a tank with hybrids and other with wilds) are wonted to pH 6.4... I don't know if is correct a hard change like this.

In the other hand.. recently I read more and more people who prefer high but stable pH levels versus acid pH.. because of work, because of complications, etc..

bs6749: yeah.. I also think the trick/weird thing is related with the KH.. so.. What do you think?.. Do you think is a mix 50/50 or 80/20 and wait for some days the parameters will be more stables?

I'm worried because I need to move my discus from my old tanks to the news, and I'm not ready :(

[DiscusLoverJeff]

If you use aged tap water and aged RO water, don't focus too much on your PH unless you have large swings. As long as your water is consistant, you will be ok.

I have separate aging barrels for my RO and tap water. The reason I separate mine is because not everyone gets both in a mix. My breeding pairs get 100% RO with some RO Right added to acheive a TDS of 75 to 80. My other fish with the 50/50 combination have a TDS between 180 to 190 (keeping in mind my tap water TDS is 275). And you can see I don't focus on PH. Although if I did, my tap water ph is 7.5 and my RO ph is between 6.4 and 6.8.

RO kh/gh are very low from zero to 1.

Consistency is what is important.

[vendetta]

Hi Jeff,

Today I'll starting mixing 50/50 combination... as you all members agree with with the consistency is more important.. so I'll choose that.

I have a doubt.. you say that your breeding pairs have only RO water, and I read in this post: http://forum.simplydiscus.com/showthread.php?25733-DO-NOT-USE-STRAIGHT-RO-WATER about problems caused because this member used 100% RO water, in an occasion he didn't do his daily change water and the pH crashed.

I can't understand what was the problem. I think you do daily water changes.. but.. do you know why the pH can change if you use only RO and not do daily changes?.

I ask this because I do 20% water changes twice per week.. and I'm not sure if a can have problems like this user.

Thanks a lot to all.. today I'll start a combination thinking more in consistency than in a low pH; and I'll tell you then how it go ;)

[DiscusLoverJeff]

When my breeding pairs have eggs and the eggs hatch, I gradually start bringing the TDS up by slowly adding tap water to my RO mix. The 100% RO with minerals added as I said using RO Right or my own mixture is only to condition the parents. It has been proven that 100% RO with a TDS between 50 and 80 will generate more eggs. Keep in mind though that after free swiiming, the TDS will get up to 180 over time, usually a week or so.

[DiscusLoverJeff]

I can't understand what was the problem. I think you do daily water changes.. but.. do you know why the pH can change if you use only RO and not do daily changes?.

I ask this because I do 20% water changes twice per week.. and I'm not sure if a can have problems like this user.

Thanks a lot to all.. today I'll start a combination thinking more in consistency than in a low pH; and I'll tell you then how it go ;)

Are you aerating your water? If you use 100 RO and your PH changes, then something else is causing that to happen. Usually after aging the water for 24 hours under aeration the parameters should be the same as your tank unless you have no air flowing in your tank?

On my breeding pairs I do between 50% to 90% water changes daily until eggs are laid. On my large display tanks, I do 50% every 2 to 3 days depending on how many fish are in the tank at that time.

[bs6749]

Water without the presence of a buffer (KH in this case) is subject to pH swings from whatever is going on in the environment. KH helps the water to resist a change in pH by reacting with the presence of an acid (from any source). It's good to have a basic knowledge of chemistry in order to proceed.

pH is a measure of the H+ ions (commonly referred to as hydronium ions) in solution. Think of acids as having a positive charge. Your KH mainly comes from carbonate ions (CO3)-2 charge, so negatively charged. KH typically comes from calcium carbonate/limestone in the ground and as such, you can safely use baking soda (sodium bicarbonate) to increase your carbonate/KH presence in the water. The calcium from calcium carbonate and the sodium from sodium bicarbonate will be present in the water as ions. They are 2 important electrolytes and will be beneficial to your fish overall.

So now we have acids with a positive charge, and KH with a negative charge. We can think of the carbonate ion as a base, and what do bases do to acids? They neutralize them. That is why you had to add so much R.O. water to see any decrease in pH with your proportional mixing experiment. You had to use up all of the base before the effects of the acid were seen. If you had absolutely no buffering capacity/no KH in the water, even a single drop of a moderately strong acid could have shifted the pH of 10 gallons of water from a pH of say 7.0 to something more like 4.0! It is the swinging of pH that can be more harmful for your fish and it is why a stable pH is more often desired.

There are some benefits of having an acidic pH of 5.5-6.0, but they aren't necessary to keep discus in my experiences.

[vendetta]

Ok, well.. I'll to mix water in 20/80 to get a pH 7... I hope it'll be a stable value.

A friend told me about desmineralized salt SERA, he adds some of it to his RO water.. I'll try mixing with tap water, and if it works I'll continue with that, if not maybe I'll try with this product.

As it is salt.. I think it increase the KH and it could be the buffer to avoid swinging.

[bs6749]

A friend told me about desmineralized salt SERA, he adds some of it to his RO water.. I'll try mixing with tap water, and if it works I'll continue with that, if not maybe I'll try with this product.

As it is salt.. I think it increase the KH and it could be the buffer to avoid swinging.

I'm not familiar with SERA and couldn't find much from searching as to the ingredients. If they aren't carbonate salts, you are not going to increase your KH. Most likely you are only increasing your GH. Like I said, if you want to increase your KH, ADD BAKING SODA.