What should I use to buffer a planted aquarium??

I have several planted tanks and I do water changes once a week but cause of all the plants the PH hovers around 6.2. Not where I would like it but our water here in Western Washington is soft and almost no disolved minearls with a PH out of the tap at 7.0. What should I use to buffer the water without messing with my plants? I don't want to use a chemical and I don't want to use anything that would hurt my plants. Can I try some coral in my filter? If I do how much per gallon of water? If anyone has any experience with this problem and would like to share I would greatly appreciate it.

why do you want to raise your PH? unfortunately with planted tanks you need to find the appropriate stock according to your PH as most plants will not survive in higher PH levels. Most SA/CA fish can handle the lower PH.

When I change water I'm using tap water which is 7.0.
after a week in my tanks it turns to 6.0.
That means when I change the water it hurts the fish to have such a drastic change in PH. If I can buffer the water just so it can stay above 6.5 then the fish will not be stressed when I give the tanks a 20-30% water change. The fish I keep can handle 7.5 to 6.5 PH with no problems but 6.0 is discus level and nothing but my angelfish can handle that. All my plants are hardy java and crypts with some moss balls and anubias plants and one tank is full of 4 different vals.

I would suggest treating your tap by letting it sit with peat moss in cut up pantyhose for a couple of days before the water change. That should lower the PH level closer to your tank levels so less stress on fish. Funny most people fight to get the PH at those levels.

It is odd but here in the Seattle area our water has very little minearls making it great for discus and angelfish but hell if you like central american or africans. I'll try the peatmoss since I already use that for my discus but isn't 6.0 too low for most aquatic plants?

I have a tank at 6 with 2.5 wpg lighting and almost anything grows in that tank. Just my experience, I have 8 soil based tanks with different lighting and ranges.

Or you could scatter a small handful of crushed coral on the bottom, that's what I do. Start with a small hand full, test in a week or 2. You will need to figure out how much it will take in your tank to get it to stay near 7.

I'll try the coral but I'll use alittle in my filter cause I have black substrate. I'll keep trac of the PH for the next 2 weeks and see where I need to dial in. Thanks for the pointer Fern-as always.

A few shells will do the same job and would look better, same thing with a small piece of holey rock.

crushed coral in ther filter would be a ok idea, or baking soda

Baking soda is iffy, it comes and goes too fast and makes the PH bounce.