How dangerous is 0 KH?

[FishySituation]

My tap water KH is 0 and sometimes it manages to climb to 40 PPM, which is still very low. Do I really need to buffer it? I wouldn’t have a problem with adding crushed coral, but I already dose equilibrium up to 150 PPM hardness and my ph is 7.5. The only time I’ve ever had a ph problem was with my 29 gallon after adding a huge driftwood piece that would drop my water to a 6.0 ph within a day after changing water. I don’t have that problem anymore and my ph is almost always an exact 7.5 when I test my tanks, so is there really any need to buffer my KH unless I add more wood or something? I do weekly 25% water changes on all my tanks and biweekly 25% changes on my betta tank. 

[varanidguy]

You definitely want to buffer somehow.

 

Crushed coral is a good option, many people resort to that because it's easy. But if you don't keep up with water changes it can also run away on you.

You can add a small amount of baking soda (there are calculators online that will tell you how much to add based on water volume to achieve a desired dKH). If you do that, make a test batch before adding it to your aquarium so you can be sure you're getting the desired amount of KH.

You can use buffering substrates which are best used with water containing zero KH. These are products like Controsoil, ADA Amazonia, Fluval Stratum, etc. They're not cheap, but they work (I would advise against Stratum, for the sake of transparency, but I have experience with Controsoil and Amazonia, both are great). These substrates can also be a boon for planted tanks as they're typically made from volcanic soil, baked, and pelletized, making them really rich in nutrients - and they will keep your water buffered to a slightly acidic pH (typically between 6.0-6.8 depending on the product). There's a lot to be said about these substrates.

There are also commercial buffering agents available, such as Seachem Acid, Neutral, and Alkaline buffers. Neutral buffer isn't recommended for a planted tank, but you get the idea.

Unless you're using an active substrate, you want to have at least 1 dKH in the water for the sake of stability.

[tolstoy21]

On 11/3/2020 at 2:39 PM, FishySituation said:

The only time I’ve ever had a ph problem was with my 29 gallon after adding a huge driftwood piece that would drop my water to a 6.0 ph within a day after changing water.

That's the problem with zero KH, there is no buffer to prevent other things from swinging it in one direction or the other. I had that happen to me with a huge chunk of bogwood in a 20 gallon, PH went under 6 over night.

For me, having no KH really comes down to what kind of fish I want to keep. I don't overly worry about it in tanks for acidic water loving fish, but I do also keep things in those tanks that prevent PH from migrating upwards, like botanicals or fluval stratum.

For all my other tanks I add crushed coral and that keeps the PH somewhere between 6.8 - 7.4 depending on tank size and how much coral I add in relation to water volume and change frequency (my change water has 0 KH). I also use aragonite sand for African cichlids that prefer something closer to, or higher than, 8 PH.

Edited November 4, 2020 by tolstoy21