Reuse fish tank water into plant only tank and back again

[Aron78]

Let me start by saying I'm quite new to the hobby. I've kept 2 African clawed frogs for a few years with no issues at all, even without water changes.... That being said keeping fish is a very different hobby altogether.
I've got a 30gal community tank going, doing weekly WC with gravel vac and my water is sparkling clear and fish seem healthy and happy. I've recently been thinking I'd like to move up to a 100gal planted tank *if I can keep this one this healthy for the next year. In the mean time I'd like to start a small tank to get the plants started.
So my question for all of you is....
Could I take the water from the fish tank and put it into the smaller planted tank. Let the plants filter and clean the water, then reuse said water back into the tank with my fish?

 

[Pharaoh]

Sure. The downside to this would be as the plants/fish use up the minerals in the water, there is no replenishment. You will cut down on your water changes, but not eliminate them completely.

 

[skjl47]

Let me start by saying I'm quite new to the hobby. I've kept 2 African clawed frogs for a few years with no issues at all, even without water changes.... That being said keeping fish is a very different hobby altogether.
I've got a 30gal community tank going, doing weekly WC with gravel vac and my water is sparkling clear and fish seem healthy and happy. I've recently been thinking I'd like to move up to a 100gal planted tank *if I can keep this one this healthy for the next year. In the mean time I'd like to start a small tank to get the plants started.
So my question for all of you is....
Could I take the water from the fish tank and put it into the smaller planted tank. Let the plants filter and clean the water, then reuse said water back into the tank with my fish?

Hello; I do not think this is a good idea. The first thing that comes to mind is the buildup of mineral salts and other such things that are dissolved in tap water. By this I mean that during each day some water evaporates from a tanks surface. The dissolved stuff in the water stays behind and will slowly increase in concentration over time. You could likely use the fish tank water in the plant only tank but I would not put the plant only tank water back into the fish tank. One of the benefits of a water change is to dillute the concentration of such things that tend to build up in a closed tank over time. The water change volume should be greater than the volume of water lost to evaporation.

I run tanks which are planted heavily. Any more I tend to run plant tanks with a few fish. The plants being the larger bio-mass. I still need to do regular water changes. In addition to the reason already mentioned there is a build up of detritus (mulm) that the plants just do not do anything about. So I use one of the gravel vacs when doing a water change. This way I remove some of the detritus with each water change.

By the way a few small fish in a planted tank will keep the mosquitoes down. You can use the tank discard water on house plants and outdoor plants.

 

[Yuki Rihwa]

Yep you can use old water for your planted tank but like Pharoah said your plants will consume all minerals so if you want to reuse the water you will have to replenishment the water minerals before put it back in your fish tank...that's quite a pain to deal with, I would do WC for your fish tank and use that water for your plantet tank and dose extra trace elements for that tank and you won't have to do any water change on that planted tank for life.

 

[verbal]

You probably would get the most nitrate reduction in a aquaponics set-up where you use plants that just have their roots in the water. Even this will reduce water changes vs. eliminating them.

 

[Aron78]

Thanks for the info guys. I never considered the minerals! This process would essentially make the water too soft over time, right?

 

[skjl47]

Thanks for the info guys. I never considered the minerals! This process would essentially make the water too soft over time, right?

Hello; I suppose much will depend on the local water and to what degree the minerals exist in the local tap or well water. I now live in an area of karst limestone.

I did live near Boiling Springs North Carolina for a couple of years and the ground water there had much less disolved minerals. In fact within a few miles of where I stayed there were native patches of pitcher plants.

My initial thinking is that my water would tend to become harder over time, but I do not have a strong confidence on this just yet.

Also it will not just be the mineral concentrations that could increase. My thinking being that while plants would use some of the things they need, anything the plants did not use would likely increase in concentration. This is a new concept to me so I may not have thought it out well enough.

 

[Wailua Boy]

I think that is an interesting idea, it may not be cost/time effective at this time. You could collect dirty water, run thru veggie filtration until nitrates are zeroed; then supplement with minerals and reuse. Even without mineral supplements the water could be used for partial water changes. If collected in an outdoor pond, annual rainfall may compensate for evaporation.