I wrote this article in 2004. At the time I couldn't afford to buy or run a reverse osmosis unit, so was looking for ways to soften water to keep discus. A simple, yet effective way to lower your pH and hardness.

Aquarium water chemistry can be one of the most frustrating aspects of fishkeeping. If you decide to adjust the water chemistry to suit the particular fish you keep, there is a cheap and highly successful method of producing large amounts of soft and acid water. Filter it over peat!!! Remember all water chemistry adjustment should be carried out away from the aquarium, hence the method detailed below. This is a simple and cheap method which should cost you less than a tenner and will produce thousands of gallons of peat filtered aquarium water. You will need:

Peat Filtering Peat Filtering Peat Filtering
Filter Floss Clean, new bucket Peat moss


Peat Filtering

What a waste of a good bucket, still it is all for the good of your aquarium fish. The bucket must be new and thoroughly rinsed. A hole needs to be drilled in the bottom, about 8- 10mm should be sufficient.


Filter floss should now be placed on the bottom of your bucket. Make sure it is a good layer, about 2- 3" thick. Remember, this will compact under the weight of the peat and the water. Make sure you give it a good rinse, preferably in hot water prior to use, this should help to rinse off any nasties.

Peat Filtering


Peat Filtering You should now fill your bucket with peat until it is about 3/4 full. Try to compact it down a bit and then add a little more. At this time you should fill a watering can or similar with hot water. Pour this over the peat and allow it to drain (onto the garden, down the drain). Once this has been done you are able to start filtering water for your aquarium.


Find yourself a suitable receptacle to suspend your peat filter over, I choose a water butt as it will hold 40 gallons. You are now ready to pour water over the peat and allow it to drain into your water butt. Depending on the size of the hole, you can reckon on about 12 gallons per hour. If you can adjust your hose to run slow enough, this is preferable to walking back and forth with a watering can. A bucket of peat this size should filter about 200 gallons of tap water, depending on your individual water supply.

Peat Filtering

Water comes out of the tap at a pH of 8.3 and with a carbonate hardness of 13, enough to stand a spoon in!! After filtering, the results are pH 5 and KH 3, quite a difference huh? As with reverse osmosis and other purification devices, it is necessary to rebuild your water to the required consistency using plain tap water. You will find that the filtered water is a "teas stained" colour. This is the tanins from the peat and is quite natural. Some people like me like the look (it is an acquired taste I grant you) as it makes the fish enhance their colouration. For those that don't like the look, a little bit of carbon run in the filter will soon clear it up.


There are a few people who have tried the peat filtering method, comments are shown below from some who have contacted me regarding their experiences:

Hi Mark,

I just tried peat filtering as per your instructions - planning to re-purpose my 70l tank for tetras and rasboras :)

Tap water readings were pH 8.6, KH 14
Peat filtered water was pH <5, KH <1

That's pretty incredible! Thanks for the info online :) Really glad I have tried it!

Flash Wilson

Below is the result of your feedback form. It was submitted by
() on Tuesday, April 15, 2003 at 03:54:14:BST

name: Dave

Hi, I've been doing the peat filtering thing for years now and think it is a remarkable and cheap way to lower the KH of the tap water. What test kit do you use to measure the KH and PH after the peat filtering. I'm wondering if my AP color match system not as accurate as it could be because of the tea colored water. Thoughts?

Thanks and you have a wonderful site.



Below is the result of your feedback form. It was submitted by
() on Monday, May 05, 2003 at 23:51:21:BST

name: Colin

Hi Mark,
I saw your peat filter and tried it.... I have to say that I was impressed with the results. I was chatting via e-mail to Dan and he mentioned your contraption and as my water is, like yours, as hard as nails I thought i would have nothing to lose! Any way, I was wondering if you would mind if I plagerised your articles on this subject for the club I belong to, it's an online club. I will rewrite it and edit it, but it is such a simple and effective way of water management that I would like to publicise it.
Thanks in advance.



Mark, thanks for the DIY section.... my German Blue Rams thank you too...
Buddy Gardner

Knoxville, TN', USA - Thursday, 05 June, 2003 at 21:16:14 (BST)