The Planted Tank Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
39 Posts
Discussion Starter · #1 ·
Hello again, I was wondering what the differences between sodium bicarbonate and calcium carbonate is. I use RO/DI water and need to bring up my KH a little. Can someone please explain to me maybe the pros and cons to them or the benefits and/or disadvantages. I am currently using Baking soda to raise my KH but I hear that it adds unnecessary sodium and that Calcium carbonate doesn't dissolve well and it is also not a significant source of calcium.
Thank you.
 

·
Premium Member
75g, 40g, 20g
Joined
·
3,848 Posts
For what it's worth, I use K2CO3 to raise the dKH in my RO water.
I agree with you that additional sodium in a planted tank is not necessary. I have not used/tried the calcium carbonate. I do know Calcium Sulfate (CASO4) does take a bit of time to dissolve.
Another tip, FWIW, I also use MGNO3 instead of KNO3. The K2CO3 does add plenty of K to the water column so there is less need for the Macros to add more K
 
  • Like
Reactions: Deanna

·
Registered
Joined
·
2,593 Posts
Like Immortal1, I've used K-based carbonate compounds (KHCO3) where relatively stable pH conditions are present. Since you said that you want to bring KH up "a little", I'd try the KHCO3 or K2CO3, first.

In my case, though, pH tends to drop well below 6.0 (I also use pressurized CO2). Since pH 6.0 is my target area, the amount of KHCO3 I would need to add gives me more K than I like. So, my approach is to use MgCO3 and, if I need more carbonates (KH), supplement with CaCO3. Both of these give more bang-for-the-buck, KH-wise, than K-based carbonate compounds. For me, both MgCO3 and CaCO3 give me all the the Mg and/or Ca I want. However, these compounds dissolve as a function of pH. At a pH of 6, I can dissolve quite a bit. As you go higher in pH, the solubility limits fall. Above, pH 7.0, you won't get much dissolution at all, whereas KHCO3 will easily dissolve.

You can find dosing results for these compounds (other than MgCO3) here: RotalaButterfly However, in the case of these carbonate compounds, solubility limits aren't shown, the way they are for other salts, because they are sensitive to pH conditions.

There sure have been a lot of KH/pH questions lately!
 

·
Registered
Joined
·
257 Posts
Sodium bicarbonate (baking soda) is inexpensive and plentiful so that's a plus, however, as you said it adds sodium which many people avoid in their planted tanks; meantime, CaCO3 due to its low solubility takes a long time to dissolve.

Good alternates are KHCO3 (what I use) and K2CO3

Lastly, there's MgCO3 but I believe it has a low solubility, too
 

·
Banned
Joined
·
628 Posts
I think you have to use KHCO3 or NaHCO3 if you want a high KH of say around 5 dKH. CaCO3 won't get you there because of its low solubility. Fisheries use between 100 to 150 ppm KH to promote nitrification in their systems. Planted tanks use less KH because "the plants like it". By this I think they mean a low KH helps the plants absorb nutrients somehow. But also that the plants benefit from having a lower pH. I've read the problem with Sodium is that it is hard for the plants to keep it out of their cells.
 

·
Premium Member
75g, 40g, 20g
Joined
·
3,848 Posts
The reason I want to raise the KH is for the fish. I have read that it is important for the proper fish growth. I could be wrong but I am not sure.
Hmmm, proper fish growth. Seems to me @Greggz has 120 gallons worth of Rainbow fish and is running 0dKH in his tank.
I have 75 gallons worth of Rainbows, Tetras, Corey cats, SAE, & Amano shrimp and I run 1dKH - never had a fish issue tied to the water that I provide.
 

·
Banned
Joined
·
6,196 Posts
Hmmm, proper fish growth. Seems to me @Greggz has 120 gallons worth of Rainbow fish and is running 0dKH in his tank.
I have 75 gallons worth of Rainbows, Tetras, Corey cats, SAE, & Amano shrimp and I run 1dKH - never had a fish issue tied to the water that I provide.
Yep the vast majority of fish don't really care about dKH.

I run mine at zero dKH and fish are healthy and long lived.

Here is a good article about low dKH tanks.

Low dKH 2hr Aquarist
 

·
Banned
Joined
·
628 Posts
Yep the vast majority of fish don't really care about dKH.

I run mine at zero dKH and fish are healthy and long lived.

Here is a good article about low dKH tanks.

Low dKH 2hr Aquarist
It's hard to argue with success. But what about buffering capacity? And why doesn't it matter? And what about nitrification if you have a lot of fish?
 
  • Like
Reactions: Greggz

·
Banned
Joined
·
6,196 Posts
It's hard to argue with success. But what about buffering capacity? And why doesn't it matter? And what about nitrification if you have a lot of fish?
pH crashes from no buffering capacity is pretty much a myth.

It's almost always caused by terrible tank maintenance, and is of no worry in a well maintained tank. I am in contact with a large group of folks from around the world, most of who run little to no dKH, and it is not something anyone I know worries about.

In my opinion, there are a lot of myths in this hobby, and this is one of them. Mostly spread by old websites that get read then folks repeat what they have read. Has little relevance in the real world.

And nitrification occurs just fine in a low dKH/pH tank. What most don't know is that most of the world runs very soft water in their tanks. Another myth that persists. My tank is pretty heavily stocked with Rainbows and ammonia is always zero.

FYI I drop my pH to 4.85 daily.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top