Basic Yet Soft

[mantella]

I just moved into a new house, and I tested the tap water for pH, KH, and GH. I came up with values of 8.2, 2, and 2 respectively. This seems unusual to me as I tend to assume basic water is hard. Is this a problem for keeping fish? I've heard that soft water is more susceptible to pH swings. Is this true? Will soft water bug fish that like basic water? Is it necessary for me to augment the hardness of my water or are there fish that can deal with such conditions? Also, will adding shells only change KH and not GH or are KH and GH intricately related?

Thanks!

 

[DrRob]

Likelihood is that it won't stay basic for all that long. Soft water is very low in buffers, so it'll move towards whatever is being created. You'll find there are a few things like hydroxide ions in the water that are causing the basic nature, but without the hardness they'll succumb to the natural acids in a tank fairly easily. Should be good water overall for soft water fish.

 

[mantella]

Thanks for such a clear answer!

I was planning on going for a minimalist hardscape made much like a well-shaded, shallow forest stream. There might not even be any driftwood present. Java fern or moss balls might find their way in, but I plan on having mostly rocks. The tank is an 8x8x30 (inches). It's shallowness may keep it from being too bare for non-schooling fish to be comfortable. The rock is mostly slate and basalt, and the substrate will be sand. In a rock-only situation will there not be enough natural acid present to make the water more acidic? I don't think either basalt or slate are that reactive with water... I could put just a tad of peat in the filter to keep is acid. Do you think that would work?

 

[DrRob]

Peat will work, livestock will tend to make things acidic over time, as will plants. Generally those rocks shouldn't cause any major pH issues, although you can never be 100% with rocks (although you can never be 100% with most things).

You used to be able to buy peat plates to put under the substrate. Haven't used them in ages, but they were good for the plants to root down into. Pain if you wanted to rescape though.