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Continuous Water Change
Is anyone using the Robotank to automate water changes?  I would like to set up a continuous water change an ml/min, few ml every 5 mins, or even a 150ml/hour.
My plan is to use the dosing pumps and run two identical peristaltic pumps off the same dosing channel.  One to pump new salt water in and one to pump out at equal rates.  The issue I see is the limits on the dosing pump.  While I can configure the system to think my pumps are less efficient then reality, I will still have to reset the bottle size frequently.

- Possible to increase the bottle size in the software?
- Possible to auto reset the bottle size?
- Possible to ignore the bottle size?
- Add a continuous water change function?

I will post my results when I get it working.

The other idea I have is to run a scheduled event 2/day by turning on AC pumps and disabling the ATO while changing water.  I will set a timer in Robotank to turn on two AC pumps and attempt to do 1/2 gallon each and twice per day.  The issue here is I'm not sure how exact or consistent over time the AC pump will be.
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Hi Mike, for a while now I've been wanting to add a auto water change system, quite a few have asked about that but not sure if anyone is doing it.

For continuous or steps I would use custom rules which are flexible, the dosing pumps have lots of issues as you pointed out.

This is a simple setup and assumes the drain for old tank water is unlimited, if not a custom rule can be added for that.

Setup a pump to drain (call it DC1) and a pump to fill (DC2) using 2 DC accessory ports, one for each pump for better control as lift height etc can change how much is pumped per min using the same pump.

Then setup a float switch at the top of tank (Sensor1) and button of reservoir (Sensor2) both on different sensor ports.

Then for the custom rules you would create 4 of them.
  • Select "Sensor1" and set "if open" and have it turn on "DC2"
  • Select "Sensor1" and set "if closed" and have it turn off "DC2"
  • Select "Sensor2" and set "if open" and have it turn on "DC1"
  • Select "Sensor2" and set "if closed" and have it turn off "DC1" and "DC2"
  • Select "sensor3" and set "if closed" and only select "send email"  (optional email alert for low level in reservoir)
With this the 2 pumps would always run unless the float in tank (sensor1) closed as in tank has too much water it would shut off pump in reservoir (DC2) and continue to pump water out of tank until "sensor1" open again and at that point "DC2" would start up again adding more water. This would continue until the reservoir was empty, and the 3rd rule would shut DC1 and DC2 off and send you an email letting you know reservoir is low. You could add a 2nd float switch in reservoir to "sensor3" port and maybe set that 3/4 in reservoir, when it hits that point it would email you letting you know the reservoir is almost empty. The rule wouldn't do anything but email you. You could also add extra float switches as backups. A cheat for backups so you don't use extra sensor ports is having multiple float switches on the same port doing the same thing and set floats side by side.

There's no limit what you can do, you could also setup switches, pumps and valves to keep the reservoir full and probably even automate the mixing of reservoir. 

Actually there is a limit today because only so many ports, this simple setup uses 2-3 sensor ports and there's only 5. With the addons I'm working on I'll probably add up to 21 sensors and a whole lot of DC accessory ports. I'm also going to add more options in the custom rules so yeah lots of improvements to come but this should get you going today.


You can adjust the flow rate of the pumps by making a small change in the code, I'll be adding this to the GUI when I upgrade the custom rules.
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glad you found this, still applies with better more options now.
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Wouldn’t it be easier to just hook up the emergency overflow to the sewage and pump in fresh water with a continuous rate?
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I agree, easier and safer but not as fun. :)
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Yeah because when you invest in a controller which would make life easier etc you still want something to keep you up at night XD
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if you going to add a continuous fresh water in and water out you will still need some kinda water conditioner like an inline charcoal filter to remove chlorine and chloramine and other metals out of the water. Where I lived before we had cold water sweet springs water was damn near perfect coming out of the ground then the city add chlorine very sad but the point is don't do like I did I just hooked up a 1/2 inch line to a auto drip and ran a 3/4 line to the bottom of the exit pipe behind a washing machine drain worked perfect but I never thought about the chlorine and it built up in my tank till one day a large school of rummy nose tetras where all dead I explained my set up to the fish store at the time and the guy checked the water with a pool test kit and the reading was very high don't remember the numbers now but that was happened to me.
Just telling the story so other people don't have to suffer like I did.
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Over here (netherlands) the use of chlorine is forbidden in drinking water applications.
So it is pretty safe just hooking op the tap water to a continuous water change system
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Canada is the opposite, any day I'm going to open my tap and get the nasty stench of chlorine, during spring they increase it a lot and smells worse than a public pool. And they have the nerve to say we have fresh tap water lol...
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Here in the states we have all kind of crape in the water chlorine is bad enough but chloramines are even worse be cause it is in a higher does would be nice to live in a place that doesn't have to dose the drinking water but also you don't worry a little about what is in your water?
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