My little 20-gal half-barrel pond has an old-timey handpump attached, with a submerged electric pump creating water flow out of the spout for a running water affect.

My goal is to keep two fantails alive and healthy. I have placed a square of 1-inch-thick filter material over the pump intake so they don't get sucked into the pump, and I've been told to rinse that off every week. Also, I top off the pond every few days. I also have a few floating plants.

Is it still necessary to replace 4 gallons on a regular basis? If so, how often? Do I need to fill 4 containers and let them sit at room temperature for a day before adding them? BTW, I have well water, so chlorine is not an issue.

Thanks!

It's not required to do small water changes but certainly will keep the pond and fish more healthy. In aquariums, I do weekly 50% water changes but for my ponds, I just top them off since I lose a lot of water due to evaporation, animals drinking, etc. For ponds, I recommend changing 30% every few weeks for smaller ponds and less for larger ponds. For those that have city water, be sure to add dechlorinator. Like you, I'm on a well. With our water, the main thing is that we want it to be similar in temperature to the water in there and aerated. Tap and well water usually have low oxygen levels and compressed carbon dioxide in the water. By aerating it well, it prevents gas bubble disease where the gases come out of solution inside the fish, and it makes sure there is enough oxygen. If changing less than 20% of the water, you don't need to aerate it. If changing up to 50%, aerating in the pond itself should suffice as it does in my aquariums. For larger changes or total cleanings, the water really needs to be well aerated for a few hours before putting animals into it. I top off my ponds straight from the hose or from the hose to bucket to pond.