mdhardy01 said:
The only reason I use R/O is I keep Asian discus which are used to softer water
Yep, soft water for fish requirements is one of those special reasons.
chump54 said:
..on a cosmetic level with straight tap water I get a massive (unsightly) build up of limescale around the top of the tank..
Cosmetics is a subjective reason, so one has to decide on cost/benefit. Again, this is not plant related.
chump54 said:
I find, but I haven't go any scientific proof that with my hard water I struggle to get the plants to pearl and I have to have the co2 sky high to get any sign of pearling at all.
I don't doubt what you report, but there's a need to consider that there is possibly some other factor involved. I and many others routinely use very hard tap water without any trouble getting the plants to pearl. In any case, although Oxygen production is an excellent measure of plant photosynthesis, pearling by itself is not, because pearling is partially dependent on a variety of other factors that are
not related to photosynthesis, but are instead related to water chemistry. Plant health and growth rate (i.e. weight gain) is the only true measure, and if one is not measuring this then everything else is potentially an optical illusion.
My point is that the OP needs to determine whether any of these issues related to aesthetics or fish requirements apply, or whether he/she was told by someone else that RO was a prerequisite for growing plants and then purchased the RO unit in response to that advice. Learning to grow plants successfully is difficult enough without the added burden of needlessly enduring the tedium and expense of RO.
Having said all that, it is entirely possibly that there are chemical agents in the tap that are of sufficient concentration to be unfriendly to plants/fish which then justifies the use of RO. Again, these agents may have nothing to do with hardness, or may be only exacerbated by hardness.
Just as in the case of nitrates, people are constantly blaming their problems on hardness. Hardness this hardness that. Few consider that there can easily be something else in their tap that causes problems. It's often just a coincidence that the water happens to be hard, so hardness gets the blame. The way to test this is to prepare pure RO water, then to remineralize using GH Booster and a carbonate salts only. In that way you've eliminated any source of tap toxin. Raise the KH/GH to high levels using the powders only and see what the differences in performance is. Then you can compare the sole effect of hardness and you results will not be tainted by the possible presence of toxins.
These plants have no trouble pearling in water KH>15 and GH>25:
Cheers,
