How can I avoid water changes with large fishes?

[aquamist666]

How can I avoid doing water changes for long periods of time with large fishes such as goldfishes, catfish, tilapia, or similar sized fish... in an indoor pond setup? Can I over filter the pond with a lot of jumbo sized filters? Will that work?

I know that some people do the Walstad method of planted tanks for freshwater aquariums with a few small fish, and some people do the macro algae with protein skimmer method for saltwater tanks. But what are the SECRET short cuts to lessen the amount of water changes in a tank with large fish? I prefer to avoid weekly maintenence.

 

[DaveKS]

Lots of lighting and lots of semi-aquatic emergent plants like red mangrove, papyrus, maybe even some water cannas. Give them good light and they will suck up nitrates and phosphates (fish manure waste) from water and turn it into plant growth. Also a nice colony of floaters like water lettuce can really clean up the water and as bonus points adult tilapia will chow down on that salad. Free super healthy green fish food.

You might also look into making a sand filter where you pump water into a container at one end, it runs through a curated (specific sand size, specific flow rate) fine sand bed with reeds etc planted in it and water that comes out other end will be nitrate, phosphate and DOC free.

 

[A201]

A lot depends on the size of the pond, the type of substrate & it's depth, decor amount & varieties, the varieties of fish and finally desired filtration.

Despite any combination of the above, periodic water changes will need to be made in a closed system.

I guess making more or less an indoor marsh pond would be the best way of prolonging the time between water changes. Unfortunately the foliage of overly planted ponds tend to obscure viewing of the fish.

 

[Mudminnow]

Can I over filter the pond with a lot of jumbo sized filters? Will that work?

Nope. Filters help convert Ammonia and Nitrite to Nitrate. So, once you have enough filtration to make these conversions, adding more filtration doesn't do anything.

But what are the SECRET short cuts to lessen the amount of water changes in a tank with large fish? I prefer to avoid weekly maintenence.

A huge volume of water with lots and lots of healthy plants should help. I'd imagine you could use examples of successful waterchangeless tanks as a model and scale up. You'd probably need to regularly remove big chunks of the plants too, so that the stuff they suck up actually leaves the system. Floating plants would probably be the easiest way to accomplish this. Also, it probably goes without saying that you'd want to avoid fish that eat plants...like tilapia.

Here's an example of a long-term, no water change, aquarium you might be able to use as a modle:

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[bgarthe]

You can also try floating algae scrubbers. These will use nutrients in the water including nitrates to grow algae. Then you harvest the algae every so often. I can provide pics if you’d like of mine in the basement 600g koi pond/tank.

 

[RayClem]

Even large bodies of water like lakes and ponds rely on water changes to keep water suitable for wildlife. The only two bodies of water I know of that do not have water changes are the Great Salt Lake in Utah and the Dead Sea on the border between Israel and Jordan. Because these bodies of water have little or no outlet other than evaporation, pollutants build up over time making these waters inhospitable to fish.

You can reduce water changes by making sure any water makeup due to evaporation is done using purified water such as distilled water, RO water, or "clean" rain water. However, unless your indoor pond is very large, is lightly stocked, and has lot of plants with exposure to direct sunlight, you will find that water changes are needed.

One thing you might do is set up a system that has essentially continuous water changes. Let water flow into the pond continuously (or at least regularly) and have an overflow either to the outside or to the sewer.

 

[FishDin]

You may want to set up a small "pond" at first to test your plan. It would be no fun to set up a several hundred gal pond only to find out you can't make your plan work.

A continuous water change systems, as mentioned, is an option. You could also set up a system to automate your water changes so that the process only involves flicking a switch. You will still need to clean filters, tend to plants, add any water treatments / additives...

 

[Gnop1950]

You can also try floating algae scrubbers. These will use nutrients in the water including nitrates to grow algae. Then you harvest the algae every so often. I can provide pics if you’d like of mine in the basement 600g koi pond/tank.

This is similar to using macroalgae in a refugium in a saltwater tank. Serves the same purpose, removing excess nutrients to prevent bad algae. Using algae to fight algae seems appropriate

But how are you topping off the pond? If it is with treated tap water, then wouldn't there be a detrimental buildup of minerals, etc., that aren't used by the plants/algae? If you use RODI water for top-offs, that avoids mineral buildup, but you may then need to supplement with trace minerals needed by the plants/fish and even beneficial algae.

I use RODI water for top-offs in my freshwater aquariums, and everyone I'm aware of uses it in their saltwater aquariums. But in both instances, I need to supplement to replace the needed trace minerals that become depleted/used over time.

The above hasn't made my tanks WC-free, but has reduced the frequency and volume of water changes I use. Right now, I do about a 10% WC about once a month.

 

[DaveKS]

A lot depends on the size of the pond, the type of substrate & it's depth, decor amount & varieties, the varieties of fish and finally desired filtration.

Despite any combination of the above, periodic water changes will need to be made in a closed system.

I guess making more or less an indoor marsh pond would be the best way of prolonging the time between water changes. Unfortunately the foliage of overly planted ponds tend to obscure viewing of the fish.

Not necessarily. If say you have a 200g indoor pond set up you can easily setup a 25g sand/bog filter along the perimeter/above edges with plants that won’t obscure/overhang main pond area. Reeds, water canna/iris are all very vertical plants that will remain out in the perimeter while outflow of sand filter dumps back into main body of water.