25% every 2 weeks for me, Gravity feed ro water to my mixing barrel next to my tank from the storage barrel mounted over my ensuite tub, add salt & heater then mix for 24 hours using a Hydor 1400 powerhead. Shut down my return pump, skimmer etc. in the sump and pump all the water out of the sump 25 gallons to the kitchen sink drain. Once emptied I pump the new water into the sump from the mixing barrel 25 gallons, making sure the salinity and temp. are good in the new water before it gets pumped to the sump. Done! No bucket carrying for me.
