You may be ok with the distilled water long term if it suits you better, you could try it for a while before buying the zerowater. Probably worth testing the GH and KH of the distilled water once just so you know that also fits in. As JayC points out (to both of us) you shouldn't need to use dechlorinator, but I understand your reluctance to chance it, I am planning to try not using it this week, but when it comes to it who knows whether I will be brave enough????
Incidently, your tank holds 14 Litres of water based on the TDS figures you gave, so my guess was spot on! Does your tank have a cover as that should slow down evaporation (and resultant TDS swinging)?
You MUST top up with just the distilled water always. The water that has evaporated has left the TDS in the tank (ie the evaporated water TDS was 000, so the TDS in the tank will have risen, then when you top up with new water (if it is TDS 000) the figure then will return to what it was before the evaporation. If you top up with water of TDS 011, then it will actually rise 1 TDS after topped up 1 litre of that water, which is small enough not to really matter as can be corrected when you next do your water change etc, and probably 1 litre may be a weeks worth of topping up anyway? If you were expecting the TDS to drop with topping up with the distilled (or even RO/Zerowater for that matter) as I think you were saying (?), it doesn't work that way - took me a while to get my head around how that works................ To slow down the speed of dropping the TDS from the 26 this time (probably a bit drastic for shrimp) it may be better to add some of the GH+ to the NEW water each time and get the new water TDS to say 100 for the new water as that will be less of a drop and you also know that some goodness is going into the tank? A female friend explained it to me thus, so this may make it clearer:
It is like making gravy in a saucepan, the water that evaporates, and is on the lid of the saucepan is pure water (clear) and the gravy still has all the gravy in it so it gets thicker (darker), when you add more water to the level it was at the start, it dilutes it back to the same consistency/colour as when you started, and you can do this all day long and it won't change colour/consistency/taste. Don't know if I am getting this over correctly but it made sense to me???????????
We had a hot summer and my shrimp survived unaffected at 26 degrees (water temperature) but 30 degrees (water temperature) has killed my shrimp in the past.I Keep a link to that video and watch it every so often as it covers virtually ALL the basics.
I had a few other thoughts on how I did my 15 Litres that I think helped:
I only cleaned the glass of the front of the tank to give the shrimps as much biofilm as possible. I also do this still with the bigger tank and it is the best way to see the babies, they graze on it. Depends on your liking etc to a degree, but generally the less you clean the sides/back may be better, ie if you can only see the front of the tank as the tank is slotted between things then best to just clean the front etc, if that makes sense?
I don't know if you have any moss but the babies seemed to appreciate that, either a small moss pad or two, and/or moss ball or two. I had 2 of each in my 15L.
Simon