Ok another lesson needed - GH

[KentFishFanUK]

Ok so in my quest to be a well informed aquarist I've been thinking about water parameters again. Trying to work out where GH fits in, I think I understand that it's a measure of dissolved minerals in the water (but not carbonates, mostly calcium and magnesium I think?) So it can go up and down independent of KH and pH right? 

I think 8° is considered about medium and obviously above is getting harder and below softer. 

I get adding anything with dissolvable minerals would obviously increase hardness, but other than RO or otherwise filtering minerals out how do you make it softer? 

When organic materials like leaf litter, wood, fish poop etc breakdown it releases acid which in turn reduces pH/KH - but does it also reduce the other minerals thus making water softer? 

Or does it only reduce carbonates thus lowering the kH but not GH? 

And if so, is there any other 'natural' ways of reducing GH without chemicals or RO water?

Thanks in advance experts!

[Scapexghost]

Plants, algae, inverts, and even fish (to a lesser extent) obsorb calcium and magnesium from the water column in order to build themselves. This will lower the hardness, albeit slowly. 

The most important thing to know about water hardness is that every commonly kept ornamental fish can handle much higher water hardness then most internet sources suggest. Hardness being to low is a more common problem. If you have hard water, fish like livebearers and african cichlids will be the easier to keep then amazon fish, but you shouldn't feel that your hard water prevents you from keeping popular amazon fish.