Originally Posted by Angel079
OK, now I can honestly admit I hadn't dealt AT ALL with water that soft, my issues before were always caused by too hard water....
Is that not too low for plants, I somehow recall something about ~4dKH ideally at the lowest, any ideas?
No, this is not too low for plants or acidic/soft water fish. In fact, you're a tad better than me. I've had fish for more than 15 years and throughout my tap water has been zero hardness (KH and GH) and acidity is now at 6.8 although prior to 2001 it was below 6 out of the tap.
I have always had a small amount (about 1/3 a cup I think) of dolomite gravel in a small nylon bag in the top filter chamber. This has consistently "buffered" my water and the GH is at 1-2 dGH and pH remains at 6.0-6.2 and for years. I replace the dolomite maybe every year, not sure I need too that often, but...it is cheap. Just regular dolomite gravel as some marine and rift lake cichlid owners use. I am told that crushed coral and marble chips also work. Limestone rock will but the effect is significantly less as limestone rock takes a long time to dissolve whereas dolomite or coral chips/gravel is a bit quicker and a very little does the job. I mention this if you are concerned and want to raise the hardness a bit.
But as you can see from my aquaria photos, I grow lush plants in this very soft water, so there is no issue with that. Most aquarium plants come from very soft and acidic water (all the swords, crypts, aponogetons, floating plants,... and several of the stem plants) so this is natural for them. Some plants have a harder time in hard water (pun not intended), Vallisneria being one of a few exceptions because it is easier for this plant to extract carbon from carbonates. Bog plants like swords and crypts find this difficult and "prefer" soft acidic water. But there is some degree of variability and adaptability, probably moreso than with fish in my opinion.
Depending upon your fish, raising the GH a tad may be a good idea. Tank-raised fish probably are more accustomed to harder water, depending upon where they are raised. I have a number of wild caught fish, and the last thing they want or can tolerate is hard water. Cardinal tetras can live for more than 10 years in soft water like you and I have out of our taps, but those with hard water rarely have such luck with this fish. And there are many other species similar. In a couple of other threads recently there have been members lamenting the fact they cannot maintain the common blue rams because of their harder water; they are undoubtedly very envious of you and me who only have to turn on our taps to fill our tanks and have these beautiful fish spawning regularly.