As some of you know I'm in the process of setting up quite a few tanks, so yesterday I decided to test the gravels and sand I intended using in some of them, to be sure they are inert.
Yesterday morning I took four clean yogurt pots and filled one with water and the other three with water plus a small amount of each gravel (thoroughly washed first). I tested pH, gH and kH on all four containers and all four read the same.
I've just re-tested and found that one of the gravels has a pH reading .2 higher than the other three containers, and that gravel, plus a second different gravel have a gH reading 1 degree higher than yesterday. The fourth container, which has sand in it, is reading identically to the plain water.
A bit of a mixed bag there - but the sand will be fine, though I'll need to rethink the gravels.
But THIS (IMO) is the most important thing to come out of these tests. I always use RO in my tanks, so wasn't aware of what my tap water is doing with pH these days. The pot with plain water had a pH of 6.6 yesterday and has risen today to 8.2. That's a massive change in pH. The water is now effectively close to 100 times more alkaline than it was yesterday.
So this is a lesson for us all as to just how important it is to test tap pH after 24 hours standing, and to choose fish to suit that changed, true level. It also shows that it is vital to draw water for water changes at least 24 hours BEFORE it's needed. Otherwise, those carefully chosen fish will suffer a massive pH shock at every water change.
Just an update to this. I left the cups standing until today, and have been testing every so often. There have been no further pH changes, but the two cups with gravels in have both risen gradually in hardness each day.
At the start, all four cups were at gH 10. After 24 hours pH in three out of four was up from 6.6 to 8.2 and to 8.4 in the fourth. Both gravel containers had gone from gH 10 to 11 in 24 hours.
Today, 5 days after the cups were filled, one of the gravel cups reads gH 13 and the other gH 15. That one is rising 1 degree a day - it's Dorset Pea gravel.
Needless to say, neither of these gravels will be going in my tanks
Hi Noodle, That's pretty interesting results. Right now I'm soon to be embarking on a tank shake up, moving all my fish, shrimp, plants and bogwood to a larger tank. I have pea-sized gravel currently, but I'm looking to go to a much much finer gravel, or perhaps even a sand if it is the best option.
Any reccommendations on what to go for?
I'm going to the same tests as you with the gravels I already have in the cupboard to see if they really are inert.
Ok thanks :) I have roman gravel at the moment, too big for my Bolivians to really shift around, I think they'd prefer something finer. I guess I won't bother testing that stuff, but I'll definitely test the other finer stuff I have out of curiosity.
So, of those sands do we know what might support vallis and various crypts?