If you are losing only 1/4" daily, it is most probably evaporation. The daily average for my area, based on USDA info, is about 0.40 inch. This is AVERAGE! Some days it is considerably higher. In some areas of the US Southwest, 3-4 inch/day loss to evap. is not uncommon. If you add plants, the average loss increases because of the loss of additional moisture due to transpiration by the plants. Also, moving water will have a higher rate of loss. So, don't despair. You have prolly corrected the original leak. Now you are left with the "unrepairable leak".....evaporation.