- This topic has 3 replies, 2 voices, and was last updated 9 years, 2 months ago by
.
-
Posts
-
In water without carbonate hardness (rainwater) of PH is very labile.
Smallest amounts of acidic or alkaline substances cause quite a change.
How high is the electrical conductivity? pre- u. after filtering?
So slight variations are usually harmless.
PH measurements in water with low conductivity are anyway difficult –
and usually wrong.Well, I think I may have answered my own question.
After searching for other instances of this problem, numerous threads and online conversations came up; other people have had problems with this as well, and it is indeed linked to the activated carbon.
Finally, one thread on a marine fishkeeping forum detailed that activated carbon can raise the pH of the water it is used on if it was not acid-washed first. At some point during the production process, ash is produced or acquired as a contaminant. Some brands/grades of activated carbon are treated with an acid wash, which dissolves the ash (ash is often composed of metal oxides), but it seems that there was also some backlash against this practice, since it could alter the pH in the “wrong direction” for certain applications and since phosphoric acid was often used, which meant that phosphates were left in the carbon and contributed to algae problems in aquaria.
The only real solution appears to be finding a brand of activated carbon that is acid-washed, or to use an acid/acidic solution to wash/rinse the carbon with prior to using it on the rainwater.
I know this is old now, but I wanted to update it with something that might be valuable to other people.
First of all, I have since stopped using activated carbon in all of my tanks, paros and otherwise. It’s too difficult to find a brand that actually will not raise pH and sponge filtration seems to be working better all around anyway.
Second, the rainwater was dirty for a few reasons. We had a very dry and hot summer, which meant that more debris and air pollution ended up sticking to the roof, and then the rain washed it down; I have since found that keeping the roof clean (or at least keeping the surfaces and gutters that contribute to one’s collection apparatus clean) by simply rinsing them with tap water from a garden hose (i.e. standing on the roof and spraying it down) goes a long way towards keep the collected water clean. I usually wait to set up the collection apparatus until the rain has had a chance to rinse away any minerals from the tap, but this does not take long under sustained moderate to heavy rainfall.
- You must be logged in to reply to this topic.