The problem is when you get above 200 ppm's that's when it's starts to affect things. If you send your water to CSI maybe and find out what is in the 500 ppm's we would find a great dif in the 300. If it works then use it but as I remember bertoxxulous was haveing a problem with the water. You also have a 40 gallon rez you were running 30 gallons in for E / F system.

If you can't buy a filter or R/O at the moment then I would buy water R/O and mix it 50/50 with your tap water to bring it down and then add half cal/mag. Not really that much water to buy. Get the filter when you can.

Or check out friends and families water with your pen you may get lucky and find a good source.