Hi,
We have used several different methods for removing chlorine from water. We've had our pond (4,500 gal) for 3 years. We probably do a 5% water change every week (not enough, I know) as a result of cleaning the filter. Occasionally we'll do a bigger one (once a month, maybe 10% ?). In City of Sacramento city limits they don't even meter our water, which I guess makes us doubly crazy to not do bigger changes.
For about the first 6 months of pond ownership we used sodium thiosulfate (ST). Then my husband for a big carbon filter, which I guess was designed for a whole house. We used that for about 2 years, changing the carbon cartridges every X number of gallons as the filter recommended. (For this purpose we got a flow meter that was like an odometer that could tell us total gallons that had flowed through the filter over its life). I could talk to my husband to figure out the brand.
Recently he got some other kind of filter which for some reason was supposed to be better (I think it just had charcoal in it)--it was smaller. only after purchasing it did he see instructions indicating that a slower flow rate resulted inmore being removed from the water. Which meant he would never put the hose on full-blast to fill the pond, so it took a while (hours) to replace the water lost from cleaning the filter. However, after having it for a few months, the flow rate through it gradually slowed to a trickle. And I mean a slow trickle. It now would take days to top off the top couple of inches of the pond. We'd get so impatient we'd just fill it with the hose, no carbon filter, and then add amquel to the pond (the powdered form comes in large buckets), which promises to remove chlorine and chloramines. Then I got some more ST, but then we went back to the old original big carbon filter (size of a car battery) but got a new one.
Now here is where my post should get really interesting and relevant to you (all that was just background!):
I just sent 3 water samples off to a water testing lab just to see what all the levels of various water components were. I collected a sample from the pond, a sample from our hose, and a sample from our hose after going through the filter. I just got the results back. I can't post an excel file on this site, so I will convert it to a .pdf tonight and post the results. It's clear to me that some stuff (Nitrate, P, K, Na, Cl) is accumulating in our pond and more frequent water changes would be in order. Sometimes it just takes hard numbers to motivate you. It's also clear that the filter reduces a lot of stuff, (like sulfur) but doesn't drop it to zero. Unfortunately the lab does not test for chlorine (or flouride). But my husband has a good LaMotte clorine test we just got. He determined that 1) there is chlorine (but no chloramine) in our tap/hose water, 2) the level goes to zero after the water goes through a
new cartrdige inour filter that's in-line with the hose, and 3) a cartridge near the end of its "life span" still reduces chlorine, but not to zero.
As I said, I can post my water test results tonight, along with the brand of carbon filter we use. I would recommend it. As to why we use that and not ST in general, I can only respond that my husband likes gadgets. I'd love to hear more peoples thoughts on the water test results.
Ellen
Camellia Koi Club
www.camelliakoi.org