automatic water change system

[ksicard]

Hey all,

I currently have a bubble magus dosing pump and I've been considering buying the extension unit, that would add 4 extra pumps to be used. On the main 3 pumps I have my ca/mg/alk supplements, and on the extensions I would setup fuel dosing, and for 2 more I wanted to do an automatic water change system. Where 1 pump would add X amount of saltwater to tank and the second pump would take the same X amount of saltwater out of the tank on a daily basis. The pumps can take a maximum amount of 2.5 gallons in and out of the tank in one day, so I guess my first step is to e-mail bubble magus and find out if the pumps can handle that on a daily basis without to much wear and tear. My second question for you guys is how long can saltwater be kept in a brute can with the lid on? And would I need a small pump like a maxi-jet for circulation? I don't want the saltwater to go bad since I would most likely make 2-4 weeks worth of water and leave it in the brute and let the pumps do the rest. And I would have my pumps add water first and then take water out second so I don't mess with my ATO sensor.

Let me know the answer if you have em, thoughts and advice are all welcome.

[eferna]

there is probably a limit for the pump to run that long. I usually do my water changes in the sump where i remove the waste that gets collected in the corners or something in the DT where I siphon the rocks now and then. By using the doser you don't have that option.

[slief]

I do automatic water changes and keep 100G of salt water on hand at all times. As long as you do something inside the container to circulate it from time to time, you will be fine. I have a circulation pump that runs for 15 minutes every 3 hours.

That said, I will provide you a bit of info with regards to using dosing pumps like the BM for automatic water changes. First, I will note that I am not familiar with the MB unit but did use a LiterMeter 3 for water changes for 3 years with good success.

There are a few things to take into consideration.

First is being able to precisely calibrate each pump individually. Due to hose length differences, water height in the holding tank vs the sump, there will be slight differences in the water volume output of each of the 2 pumps used for adding and removing the water. If there are any variences between the flow rate of water out vs water in, that will have a direct impact on salinity over time. Too much in and salinity will climb, too little in and salinity will drop as the ATO will compensate. Thus regular precise calibration is very important when using dosing pumps.

Second consideration is the fact that dosing pumps are very slow. In my case, I was changing out 3.7G per day using my Litermeter which with a dosing pump would be a long and slow process. The Litermeter would break that volume up into small short intervals dozens of times a day. With many dosing pumps, that process would be done in one long slow run.

Last thing is maintenance. The biggest issue that you may encounter is the hoses in the pump wearing out. With an automated water change process, that is something you have to pay particular attention to. Not only will hose wear effect the calibration which can lead to changes in salinity but it can also result in a leak if either hose cracks from wear and tear which in turn can cause bigger issues.

While my Litermeter III water change setup served me very well, I have since swithced to the Genesis Renew which is a bit more fool proof and is completely maintenance free. I changed because I got tired of the regular maintenance that was required with the Litermeter to keep it precise when used for automated water changes.

Others have suggested using dual head medical dosing pumps which seem like a good idea as well. While they may be so, they are designed for continuous operation. What I have often wondered out those devices and in particular the dual head ones is how hose length and head pressure effects the output from one hose to the next.

[slief]

One other thing to consider. You mentioned that you would pump water in first so you don't mess with your ATO. Not knowing how large you sump is and the protein skimmer you are using, I think it is important to point out that 2.5 additional gallons in your sump could impact your skimmers performance and in some cases could cause it to overflow depending on the sump size and your skimmer type and its current settings.