Peat moss substrate for amazonian tank?

I would like to try using some peat as an amazonian tank's base... but I am worried it won't turn out well due to the low ph and possible fluctuations in hardness after using this...
Any ideas as to what may happen?

Hardness out of the tap is around 100-120 so its pretty soft.

I've done it. I found it okay if not deep, as gases built up otherwise. It is a slowly decomposing substrate. It is messy, cloudy and not very effective at modifying the water. It gets spent fairly fast.

Under a substrate it works better, but for the decomposition. They used to sell peat plates - compressed peat that could be put on the tank bottom under gravel. That was good as a plant food source.

I prefer treating the water with peat and using a neutral substrate in rainforest tanks. It helps to control the unavoidable mess.

Complete agreement with the man with the gruesome avatar (apologies if the remark offends). What is that thing Gary ???

Condition the water using peat in an outside reservoir is better than having the decomposing peat inside the tank. Gardeners love peat for the same reasons we should avoid it. Decomposition, nitrogen release, carbon source relatively uncontrolled. I used a large garbage pail to condition my water using peat in a sack so that the peat is not adding particulate into the water. Filtered after taking from the reservoir to ensure water clarity.
I remember the peat plates and they were quite different from the gardener peat. Where they went I do not know. Amazonian water I tried to replicate with peat as well as tannin source (ie wood). Wood in the reservoir may help leach and age, but not sure of the biological process here. As well, Amazonian water is akin to runoff. Therefore perhaps consider plants that are high nitrogen metabolizers, somewhat like the marshland effect along the St Laurence.
It has been awhile since I treated for pH. You may have to neutralizer the carbonates in our water, which I have not done recently.

I have used peat in my 120, a layer on the bottom and then unscented kitty litter (read the ingredients... it's great for planted tanks - clay and diatomaceous earth) and then fluorite on top..... things went well until the anaerobic gases built up and blew up the substrate..... it settled down though and was fine.... until the geos decided to spawn and tear things apart down to the tank bottom....

I generally use RO water now and then add lots of leaves (almond, oak and beech) along with alder cones and sometimes a bit of "Black Water Extract - there are several brands.... much easier and cleaner with my sand bottoms....