We have been using a 1G poland spring water jug (or any jug). Cut away the bottom of it and turn it upside down so it looks vaguely like a funnel, drill a couple of holes in the cap to let out the water, stuff some pillow floss down near the bottom to catch loose particles, and pile on several inches of peat moss. It's a crude filter, and we just directly pour water through it into a bucket/tank. It's very fast and takes down the pH of our city water from ~9 to ~6. Have to replace the peat every 20 or so gallons of water you pour through, but it's pretty easy.
Just did this, brought my 8.2 pH tap water (was 7.2 until recently) down to 6.2. I'm going to have to mix with some 8.2 tap water to get it higher. My neo's and Tigers especially aren't digging the 8.2. Hoping a 50/50 mix will get it near 7 and make the tigers and neo's happy. Got a HUGE bag of peat for like $6. Should last for a while until I can get a RO until.
Just tested, it's taken my 8.2pH 8gH 240 TDS tap water to 6.2pH 5gH 135 TDS. Perfect Crystal water. lol. I took a container, cut a hole, put floss in the bottom, then carbon, then a phosphate absorbing pad, ammonia absorbing pad (I bought tonnes of these at Big Al's at 75% off a while and never used them) so it should be removing any phosphates in my local water and nitrates in the water, carbon removing anything bad as well. Beats having to buy RO jugs right now and lug them up 3 flights of stairs and the waste of 4-1 for an RO unit is putting me off one, we use too much water at our place as it is and pay a premium for the amount we use. Going to setup a 10gal with some inert sub and water and try some low grade crystals in it.