Phosphate vs. bicarbonate pH buffer - RODI water

[Pylor]

I made a post a bit ago about the water in my new apartment having a pH of 9.5 according to my soon-to-be water company. In preparation for this I've bought an RODI unit to create livable water for my upcoming community tank that was decommissioned 7 years ago.

Seachem offers two different products to buffer the pH of RODI water, one of which is phosphate based (supposedly stronger, but worse for plants due to algae?) and one which is bicarbonate based (weaker? Better for plants). I'm not super concerned with growing plants; I'll put some java moss in the tank probably and maybe eventually java fern as I have low lighting (20 watts for a 29 gallon tank) and no C02 equipment. I'd like to have the java moss grow but the fish are much more important to me. I'm wondering if anyone has any experience with the two types of pH buffering products. I'll be using the seachem equilibrium to remineralize the water, though I find it odd that the equilibrium has no salt at all while the replenish does. I figured some salt would be good for osmoregulation...

 

[threnjen]

I am NO expert on this so take my response with a grain of salt. I have extremely soft water, so soft it's practically RO. I was advised by several people to remineralize with Equilibrium.

As for pH buffer, your RO should help with this so that you shouldn't need to use the chemicals. Adding chems to fix pH is usually an ongoing exercise in frustration.

 

[Brookster123]

You could buffer with limestone or crushed coral as well.

 

[Pylor]

From my reading, RO water is essentially water with nothing in it, pure (or close to) H20, which is extremely volatile in pH as it has nothing dissolved in it to buffer. The reason people have so much trouble altering water is that they use tap water which generally contains decent amounts of calcium carbonate, which increases both carbon hardness (KH - which is buffering capacity for bicarbonate based buffering systems) and general hardness (GH - which is dissolved concentration of calcium and magnesium).

Thus, RO water, with no buffering capability, requires some sort of (either carbon or phosphate) buffer to be added, much like what a water company does that causes people so many problems altering their pH

Brookster mentions crushed coral or limestone which are both made of calcium carbonate and would indeed raise my KH (and GH)

 

[threnjen]

I apologize - I was misreading/misinterpreting. I was thinking you meant pH alteration but I understand now you meant pH buffering (kH). I realize this is exactly what you said, I just read it incorrectly.
Keep in mind that crushed coral is going to raise your pH. Its kind of a fine line to walk. Unfortunately anything that raises your gH/kH tends to raise your pH as well.

 

[Mebbid]

There are two options when using RO water for a freshwater aquarium.

1. Mix a % of tap water with it to reach the desired pH and kH. This has the benefit of adding other minerals to the water that fish need rather than just pH buffers. There are quite a few nutrients in the water that crushed coral, limestone, or any other way to buffer pH won't add.

2. Seachem Equillibrium - This has the benefit of allowing you to easily mix all the water to a specific pH. It also contains all the nutrients needed for fish.

I would highly suggest against using pure RO water and just attempting to buffer the pH.

 

[Pylor]

Thanks for all the feedback guys, appreciate it!

Mebbid, I actually put (at the very tail end of my very long post, so I can see how it'd be easily missed) that I was planning on using equilibrium to remineralize the water. I wonder if I should also add some "fresh trace" to the system as well. If I'm going to go with RO water, I'd prefer to just stick with it; I don't have a ton of gallons in terms of fish tanks so I don't mind paying 15 bucks every 6 months to regulate my tanks well and protect them against the horrid water I'm moving into.

 

[Mebbid]

Yep, you certainly did say that! My eyes tend to glaze over with reading nowadays since I spend hours upon hours reading school text books.. Not to mention my brain has turned to goo

I understand what you're asking now. If you planned on eventually moving up to adding more low light plants than just a java fern and some java moss then I would go with the equilibrium. If you're gonna stick with just those and focus on fish then I would choose the Replenish instead.

Any further addition of buffers or additives on top of that should be unnecessary.

 

[Pylor]

Mebbid, or anyone else for that matter, what do you feel the benefits of replenish is over equalibrium? I've looked around the net and the only thing I can find is that replenish has some salt that might be bad for fish.

 

[Mebbid]

At .7% the salt content of the replenish is completely miniscule. My math is probably wrong since I'm doing it in my head and its my bed time but I'm going to give it a try. There is 7ml of salt for the entire liter of replenish. Diluted at 5ml / 10 gallons. 200 10 gallon doses of the replenish in the bottle giving a .003 whatever % of salt in the dilluted dose. Tap water by comparison can have up to a recommended .002% of sodium with well water potentially containing a much higher level.

The .002% is at 20mg / liter. While the recommended dose of aquarium salt is 600mg ish/ liter

 

[Pylor]

So you're saying the salt added from the replenish isn't a big deal either way then? I'm just curious as to why they make two products, that's the big thing that gets me. They advertise one for community tanks, and one for planted tanks. It makes me feel like I'd be sacrificing mineral reconstitution for fish if I went with the equilibrium, though if you look at what minerals it contains, it's got quite a bit different stats for some of them than replenish.

I made a post on the seachem forums, hopefully they can recommend the correct product for my situation with a strong reasoning (not that you haven't made a recommendation, I just still don't get why replenish exists if equilibrium is "good enough" for fish too, if that makes sense), Maybe it's as simple as "these minerals aren't needed without plants" and that's it.