Well the cheapest long term answer to your problem is to get yourself an RO
unit. A unit might cost, say 100 bucks. But when you can get distilled water from your grocery store sometimes as high as a dollar a gallon it can add up quickly. In my 55 gallon I have a gallon of evaporation happen daily in my tank, so that is a gallon I have to put back in and this isn't even considering the weekly min 5 gallon water change. That is 20 gallons a week at ~20 dollars. Getting an RO
unit will pay for itself in just over a month.
If you are going to hold firm at where you are at now in terms of livestock, you might be able to get away with not getting one for alittle while, but I would recommend you get one asap to prevent the nitrates from building up to levels that it kills off your livestock. I'd be worried about the shrimp as they are not very tolerable to low levels, let alone high.
Check out bulkreefsupply or ebay for a cheap unit to get yourself started.