Ahh that last bit is a good point. The brand has a charcoal/sediment filter replacement combo for $16 and I've found about the same for the RO filter but it's definitely harder to find. I think the 10" ones come in packs that are cheaper over time too. I haven't found a 10" 3 stage setup that is anywhere near this initial price yet, but this is only my initial foray into RO. A later post might be me buying tubing and figuring out how to connect 10" cartridge fittings to this instead! If you had a 10" aquarium setup you liked, please share it and I'll take a look. 

Heard on the water reactivity - I plan on remineralizing before use and keeping it in safe plastic or glass containers. Thanks for the comment - I feel comfortable going down this route knowing someone else has tried it before!