Im trying to do everything in the following link in my 30g. Its how to mineralize soil for a planted tank.
How-To: Mineralized Soil Substrate, by Aaron Talbot - Library - Aquatic Plant Central

Basically he mixes clay with the soil for the plant roots to get iron. BUT my water is pretty hard as it is. Wouldnt the iron make the water harder or would it stay in the clay?

He also adds calcium, magnesium and potassium to help the plants. Same question. Would it effect water hardness?

Wouldnt the plants get all those minerals out of the hard water?

Thanks any help would be awesome!

hmm im not sure,i use iron tablets and my waters pretty hard too but it doesnt seem to effect it.my waters well water and its pretty hard.so i don't think it would.do you have a liquid test kit that tests water hardess?you could always do a test and put it in and see.

and what i mean by this is by putting the stuff in a cup,then put your water in a cup and wait a week or even 3 days and test your water after,this way you dont have to completely start over if it does effect the hardness.

The kh is mainly a function of the carbonate ion and gh is a function of calcium and magnesium.

It is possible for plants to become iron deficient and especially macro algaes in a marine tank. But less so for a freshwater tank

So I don't think iron from pottery or baked clay substrates will affect hardness much at all.

FWIW I use ferris gluconate pills from wallgreens to dose very very low levels of iron. I dissolve a pill in an old coke bottle of water (12-20oz) then add 1/2 to 1 capful each week. Hopefully that is enough to prevent plant iron starvation but not enough to raise the iron significantly over a few years or so.

I also don't use mineralized soil but to use 1" peat moss, 1" play sand and 1" pc select for a substrate. I use the sand to trap on the peat moss by wetting the peat moss the putting the sand on top. The peat moss is the 1'x1'x3' plastic cubes from lowes labeled canadain spaghnum peat moss (as near as I can spell it anyway) with no ferts added. Not the small bags for potted plants that do have fertz added.

From what I have read about mineralized soil I just may be making mineralized soil in tank with that method. The moss costs $11 per "bale, sand is $2-3 for a 50 ppound bag, and pc select is $8 for a 50 pound bag. So it is very inexpensive and the tank is setup and running with plants within hours.

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

The method may work well, but from what I have read about MTS the peat moss isn't going to be able to match what you add in the making of MTS. It may have some of the same ingredients, but not much different than plant specific substrates available for purchase like Eco-complete. MTS essentially takes the place of adding ferts to the substrate (not all people do it and plants still thrive) like many people do. In the low tech world you essentially are not adding anything to the substrate or water column and if the tank is hi-tech lower ferts are needed.

Whether or not the plants get enough of those things out of the water is a may be a matter of how much of each is in your tap. Seems like Calcium and Mag would increase water hardness or gh.

actually hardness did increase to very high values when I used just a play sand substrate. In one tank that had been running for over 5 years kH was 19 degrees and gh was 35 degrees (or more). Tank was a 10g and had 30 guppies over vairous sizes including 1/2 dozen reproducing adults. Those fish had grown up from the original cycle trio. And I did occasionally (once a year or so) just harvest 1/2 dozen fish for other hobbiests. Now 10 years later some of those fish are in a local doctor's waiting room tank.

but neons did not survive long in that tank.

But with peat moss neons survived and kh was 4 degrees and gh was 9 degrees constant for over 2 years.

In both tanks the plants did very well.

still just my .02

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

Then I would say that your layered method supports your practice of no filter or water change then. gh and kh will continue to climb in tanks to a certain level without water changes. A decent water change can have a sort of reset effect, if you will. I can believe the values you gave, especially if that tank never experienced water changes during those 5yrs.