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A Different Kind of “Water Change”?


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After a rather traumatic incident where about a third of my fish died during/after a water change and the reality of changing 250+ gallons of water per week setting in, I’ve had an idea…

Between a cheap transfer pump pumping tank water outside into the yard and a garden house permanently hooked up to my laundry room sink, I’m getting pretty fast at water changes. But, I can’t help but thinking that it could be more efficient, especially when it still takes nearly an hour to water change each of my 125s once a week  

What if, instead of my usual method of draining the water down with a pump/siphon and refilling, what if I did both at the same time? I could start a siphon on one side of the tank and fill on the other (using dechlorinator of course), dialing in both with hose valves to keep the water level somewhere around the same. Run each for a set amount of time, depending on tank size, maybe gravel vac in the meantime and boom, you’re done. It’s pretty much just like what you fancy auto water change people are doing isn’t it? I realize your water is aged/dechlorinated beforehand, though.

Advantages to this approach:

Less stress on the fish hopefully, because the water level isn’t lowered. Also, less (albeit minimal anyway) bacteria die-off for the same reason.

I can keep heaters and, more importantly, filters running the whole time, especially hang on backs or canisters if the don’t need cleaning. Again, reduced potential bacteria die-off.

More gradual acclimation to fresh water if PH levels are different. I don’t know how long crushed corral takes to buffer, but at least it gets a head start, especially if it’s in the filter like mine is.

Less risk of overfilling as long as inflow (mostly) matches outflow and I leave a couple inches of buffer.

Possible disadvantages:

Potential of too much water being changed out if I get busy with other things and forget. But at least I could set a timer to remind myself rather than just having to watch to see when it’s full and overflowing if I forget. 

Potentially somewhat wasteful of water and dechlorinator since I’m draining/filling at the same time. This could be mitigated by setting the timer for slightly more time than it would take just to fill and dosing dechlorinator initially and then again once the tank is done “filling”

I’ve tried it on a couple tanks and it seems to work well. Has anybody experimented with this kind of approach before? Am I missing any potential pitfalls of problems that could arise?

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Sounds fine how are you dechlorinating. If you are adding it before you start adding new water and siphoning away at the same time you are removing your dechlorinating agent. I see no real issue here because you can add more at the end as long as you are not having high tap chlorine. My water company randomly shocks so I can get up to a 4ppm reading which would concern me but if so you could add more dechlorinating agent mid way. If you are in need of drastic nitrate, ammonia or nitrite, medication/bacterial illness removal this method would not be efficient or as affective but if you are just doing the weekly to give fresh water I don’t see an issue. 

My issue is I’m easily distracted …squirrel…🤣 and that’s a lot of moving parts and water so would most definitely mean overflows for me  


Edited by Guppysnail
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It feels like it would take more fresh water to provide the same mix of old and new as you are removing some new water with the old water all the time. 

But I agree with @lefty o that does sound like a punishing water change schedule have looked at ways of reducing frequency or volume instead, I only do larges changes (30% or more ) if there has been a problem or I'm planning to be away for awhile, I generally do a 25% every 6 to 8 weeks on my 60 us gal if the parameters tell me to. 

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At a glance, the only problem I see with your water exchange, is that you are pumping out the new water as well as the old water.  If you manage to balance water volume  in/out, I would think that as much half of the new water is going down the drain.  I don't think that water level changes for a short period are much of a stress factor.  Rewarding the occupants with a light feeding afterwards can help eliminate their stress.

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