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Hi,

I recently purchased an RO/DI unit for my 3 L-134's and 3 L-182's in an attempt to help lower my PH levels, TDS, and hopefully produce some spawning behavior. My tap water is consistently around: (PH: 7.6-8.2, GH: 8 degrees, KH: 5 degrees, and TDS: 135) and this is currently the parameters that both my L-134's and L-182's are in within their 20 gallon long tanks. Last night, I tested out some different tap water/RO/DI mixes in a 5 gallon bucket and got the following results: (1/2 tap & 1/2 RO/DI: PH: 7.4 - 7.6, GH: 4 degrees, KH: 3 degrees, and TDS: 61) & (3/4 tap & 1/4 RO/DI: PH: 7.8 - 8.0, GH: 5 degrees, KH: 4 degrees, and TDS: 107).

The PH levels on both of these mixes was higher than I was expecting, seeing that the pure RO/DI water had a PH: 6.4 - 6.6. My main goal is to lower my PH to around 6.5 - 7.0, while maintaining a relatively stable KH so that I don't experience any large PH swings. Furthermore, I do not want to cause more harm than good by "chasing the perfect PH, TDS, etc" So I'm really looking for any advice that will help lower my PH into a more acceptable range for these species, while maintaining the appropriate GH/KH/TDS levels as well.

Therefore, I guess the main questions I have are: 1.) What mix of RO/DI/tap water has worked for you guys?, 2.) Is cutting the RO/DI water with tap water sufficient enough? Or do I need to remineralize it some other way? (I have read that equilibrium is useful for planted tanks but I am most concerned about the well-being of my plecos), 3.) How should I go about adding the tap water/RO/DI mix to my tanks for the next water change? What percentage of RO/DI/Tap water mix should I start with and how much? (I do not want to shock my plecos, which are currently in water with a relatively high, but stable, PH), 4.) What should my target KH, GH, PH, and TDS levels be for the RO/DI/tap water mix and eventually for my tanks that are currently holding my plecos? (I do not want to remove too many of the healthy minerals within my tap water or alter the KH so much that it causes large PH swings), and 5.) Does anyone have experience using peat moss within their filters to help lower the PH? What brands have worked best for you?

Also, both of the tanks have several anubias, java fern, and amazon swords within them so I do not want to add so much RO/DI that it ends up removing too many of the healthy minerals and then killing my plants. The substrate within both of these tanks is 1/2 pool filter sand and 1/2 eco complete (I recently added the eco complete and feel like that may be elevating my PH levels a bit). I have several pieces of drift wood and around 4-5 almond/catappa leaves within each tank (both of which never really altered my PH at all when using just tap water & and I believe that is due to the relatively high KH level within my tap water).

Sorry for all of the questions but the only information I have really come across online regarding RO/DI water for freshwater aquariums is for shrimp. Therefore, I'm hoping some of you pleco experts (hopefully someone who has experience breeding L-134's or L-182's) can help me with this dilemma. Furthermore, I realize that everyones tap water parameters are different but If you guys could give me any sort of insight into what has worked for you or things to totally avoid when using RO/DI water, it would be greatly appreciated.

-Thank you.

Welcome to PlanetCatfish .

Firstly, I'd recommend starting with a 50/50 mix, I'd pre-mix it in a bucket/suitable container, then use a small pump or a hose to siphon it in, if you can position the bucket higher than the tank to refill.

Then you can monitor the parameters of the tank for a couple weeks and adjust the mix from there. You will probably have all the additional minerals, etc. in your tap water, I wouldn't worry about adding anything other than tap and RO water to the mix, except de-chlorinator to the tap water.

That said, I went through a similar exercise with my L134 several years ago, softer water, dry/wet seasons, more food, less food, etc. then I got bored of the extra effort for no return. I just used tap water from then on, a few months later they spawned !

Now I have a fish room, my formula is 20-30% HMA filtered tap water to 70-80% rainwater, if it's not rained recently that'll be replaced with RO. Although my tap water is much harder than yours, 2- 3 times, depending on when it's measured.

Good luck with them.

MarcW wrote: 20 Apr 2020, 18:42 Welcome to PlanetCatfish .

Firstly, I'd recommend starting with a 50/50 mix, I'd pre-mix it in a bucket/suitable container, then use a small pump or a hose to siphon it in, if you can position the bucket higher than the tank to refill.

Then you can monitor the parameters of the tank for a couple weeks and adjust the mix from there. You will probably have all the additional minerals, etc. in your tap water, I wouldn't worry about adding anything other than tap and RO water to the mix, except de-chlorinator to the tap water.

That said, I went through a similar exercise with my L134 several years ago, softer water, dry/wet seasons, more food, less food, etc. then I got bored of the extra effort for no return. I just used tap water from then on, a few months later they spawned !

Now I have a fish room, my formula is 20-30% HMA filtered tap water to 70-80% rainwater, if it's not rained recently that'll be replaced with RO. Although my tap water is much harder than yours, 2- 3 times, depending on when it's measured.

Good luck with them.

Thank you for the reply! I'll start with the 50/50 split and go from there. Hopefully this will be the trigger they need to start spawning.

Hi all,

Bcast077 wrote: 20 Apr 2020, 16:58......The PH levels on both of these mixes was higher than I was expecting, seeing that the pure RO/DI water had a PH: 6.4 - 6.6. My main goal is to lower my PH to around 6.5 - 7.0, while maintaining a relatively stable KH so that I don't experience any large PH swings. .........

You don't need to worry.

You can't really achieve what you want with out adding pH buffers, and that is an entirely pointless exercise. The problem is with pH as a measurement, it is both a log^10 value and a ratio. This means that pH always needs some interpretation, because you can record similar pH values in waters that are chemically very different from each other.

As your water becomes softer (the dKH falls) pH becomes more and more unstable, this isn't a problem, it is exactly what happens in nature.

Have a look at the water paramaters from Rocha, RRA.; Thomaz, SM.*; Carvalho, P. & Gomes, LC. (2007) Modeling chlorophyll-α and dissolved oxygen concentration in tropical floodplain lakes (Paraná River, Brazil) Brazilian Journal of Biology 69:2



Because of the nature of pH I use a different approach, where I use conductivity (ppm TDS) as my datum value. The advantage of conductivity is that it is a linear measure, and you can measure it accurately with a relatively cheap meter.

I'll put in the chemistry bit, for those who might want it.

When you reach pure H2O pH is a fundamentally meaningless parameter. When we talk about water (with any dKH value), we aren't really talking about water, we are talking about a dilute solution of carbonate salt(s) with H2O as a solvent.

When we talk about dKH we are referring to the carbonate part of the carbonate ~ CO2 ~ pH equilibrium.

Limestone (calcium carbonate (CaCO3)) isn't soluble in water, but it is soluble in weak acids and pure H2O ("RO water") is a weak acid because it absorbs CO2 from the atmosphere, and then 0.15% of that CO2 becomes carbonic acid, H2CO3, which disassociates into HCO3- and H+ ions, acids are defined as H+ ion donors, you've added an acid and the pH falls. The amount of CO2 dissolved depends on the atmospheric level via Henry's law.

You always have the same amount of Total Inorganic Carbon (TIC) based on the atmospheric level of CO2 (and its solubility at a given temperature), but whether you have CO2, HCO3- or CO2 is pH dependent, as part of the carbonate ~ CO2 ~ pH equilibrium.



cheers Darrel

[/quote]
Because of the nature of pH I use a different approach, where I use conductivity (ppm TDS) as my datum value. The advantage of conductivity is that it is a linear measure, and you can measure it accurately with a relatively cheap meter.
[/quote]

Very interesting, thank you for the reply. If thats the case, what is the target TDS range you would recommend for these species?

-Brian

Hi all,

Bcast077 wrote: 20 Apr 2020, 22:16Very interesting, thank you for the reply. If thats the case, what is the target TDS range you would recommend for these species?

I haven't kept L134 or L182, but I grew out and using this approach, and have had sp. spawn successfully.

I use rainwater and have planted tanks. I keep these in the range of 100 - 140 microS, so about 60 - 100 ppm TDS.

There isn't anything magical about the conductivity figures, they are just that our rainwater has some carbonate buffering.

cheers Darrel

My suggestion would be to stop overthinking it..... I do use a 50/50 of tap to RO water for mine. Trying to simulate exactly what they would have in the wild isn't needed and will likely just cause you more problems than help. Adding some wood for tannins will help lower the PH but if you use to much RO it can drop the PH to much to fast too. Have patience.... give them time, play with the temp and do a dry/rainy season and that may trigger them.

HTH
Chuck

stuby wrote: 21 Apr 2020, 13:28 My suggestion would be to stop overthinking it..... I do use a 50/50 of tap to RO water for mine. Trying to simulate exactly what they would have in the wild isn't needed and will likely just cause you more problems than help. Adding some wood for tannins will help lower the PH but if you use to much RO it can drop the PH to much to fast too. Have patience.... give them time, play with the temp and do a dry/rainy season and that may trigger them.

HTH
Chuck

Thank you for the reply. That's what I'm starting to think also haha good to hear it from someone else though.

-Brian

Hi all,

stuby wrote: 21 Apr 2020, 13:28My suggestion would be to stop overthinking it..... I do use a 50/50 of tap to RO water for mine.

I'd agree, probably start there and see what happens.

cheers Darrel