I see, that is good news in at least one aspect...you should be able to acclimate a pleco to your hard water without problems; which would be the 'safer' bet since it may prove to be somewhat 'tricky' to constantly maintain the same water chemistry all the time...and even if you use all RO water, you would then have to use products which would replace the needed trace elements since RO water, like Distilled water, is pure water or 'dead' water, meaning there isn't much, or anything, that will help support life in great amounts.
In fact, you can acclimate most any freshwater fish to a wide range of water chemistry, including an 'unnatural' pH, Gh, and Kh without putting them at a serious disadvantage. Even breeding is not an issue with most fish, however in some cases, those parameters might be more necessary than with others (an example might be discus). For example, I kept Malawi Cichlids in my tank with a relatively low Gh and Kh, as well as a pH of about 7.2 to 7.4 and wound up with more fry than I could give away...even though in Lake Malawi, the water chemistry is much different.
Even though this article might refer to saltwater livestock more than anything else, they are all practices and methods in which we can all use, even with freshwater livestock, to ensure that they are acclimated and able to avoid problems like osmotic shock and just general stress (which can easily lead to an entire dictionary of other problems/illnesses/diseases). To read that article, browse through the 'maintenance' articles of the
Articles section by using that link, the link in the upper left hand corner of this, or any other forum page, the link in my signature below, or by clicking
HERE to directly to the acclimation article.
Hope this helps. It is good to see someone who has a fondness for plecos above and beyond feeling like we need them for algae control alone. I hope that you can also share some pictures with us as well!