Artificial pond into natural ecosystem with carnivorous fish

[NetMax]

Similar post in Native fishes to get species-specific advice, but re-posting here for pond eco-system specific advice.

Basically, a fishless pond is easy as the nitrogen products balance themselves (plants consume, die, decay into plant food). The nitrogen products also drive the food chain for all sorts of micro-organisms, bugs etc. However, what is food for plants is poison for fish, so introducing fish tends to eventually unbalance a natural system unless it's quite large. With filters, we can push the nitrogen products (ammonia, ammonium, nitrites) into less-toxic (for fish) nitrates (NO3), but these systems need human intervention to remove the build up of NO3 (water changes, removing excess plant growth, wetland filters etc). Nothing new there, so here's my challenge - I want to convert a 20,000g in-ground pool into a 20,000g pond for native fish (Yellow Perch), with a significant food-chain for the Perch, not requiring a lot of maintenance or human intervention.

For filtration, I'm going with a 60sq.ft bog filter. For circulation, a 1/2 & 1HP pump. For water changes, I'm landscaping for run-off to provide (after evaporation) a 30% water change/month, with 1/3 of that coming from concrete pavers to maintain kH/pH during rainfall. For zones, the kidney-shaped pool/pond (45 mil EDPM liner) has a 39" deep 5,000g section (will be planted, pot & floating), waterfall return - and a 9' deep 15,000g section with bottom drain and pond skimmer. I'm investigating the possibility of using biocenosis baskets to create a leaky separation between the 5K from the 15K zones (for NO3 reduction, contain leaf litter & floating plants). The 5K zone will also be the spawning ground and fry grow-out. Climate zone is 5a (Ontario), and the plan is to run 2023 to vet the equipment setup and establish the biomes, then introduce fish in 2024 (self-replicating feeder fish), and possibly 2025 for the Perch (which are carnivores, insectivores and filter-feeders so they can reach deep into the food chain).

My dilemma is a) how to approach finding the right balance in water parameters to support the food chain AND provide high quality water parameters for the fish to prosper, and b) what micro-organisms, micro-fauna can be supported in an environment which freezes over for 1/2 the year.

I'm approaching the biome issue by seeding with mud from local ponds/lakes, and I'll see what I get. However an artificial (bare-bottom pond) will not support the required diversity, so I'll need to provide some type of a leaf litter/substrate environment in the 5K section (also to support spawning/fry development etc). I'm planning on only having about 25 Perch, so I don't worry about predation of their fry, and I'm more worried about predation of their food's fry.

My experience is in keeping water parameters free of nitrogen products for fish, so shoveling leaves 'into' a pond seems very counter-productive for water parameters but a requirement for their food chain.

I expect to supply them with some food (I don't think 20,000g is large enough for 25 10" carnivores to be self sufficient), though training them on pellets might be a chore and I don't know how much of an appetite I have to keep them in live & frozen foods.

I'll create enough hiding spots in the 5K zone, using plastic pallets, large stones etc, and I'm leaning towards not having a substrate, but concede I'll need some type of organic base like leaf litter. The bottom drain in the 15K side will have a large stainless steel 1/4" mesh sieve.

My more-obvious questions are:

1) Do Yellow Perch (or any comparable native fish) over-winter in a torpor state (like Koi at around 10C/50F) or do they just reduce their activity level (meaning I'll probably need to feed them at some point in the winter)?
2) With my setup & climate, what would you recommend I establish into their food chain (cray, frogs, smaller fish etc)?
3) Does anyone have anecdotal or real data on the effects of specific organic decompositions on water parameters? I can remove all live/wilting plant matter in the Fall to prevent decomposition, and I'm thinking dried leaves might be mostly fiber, and dried branches would not significantly contribute to nitrogen waste.

Ideally is there an NO3 sweet spot, (eg: 15ppm) that is safe for native fish AND supports their food-supply biome (or am I trying to do too much in this size of a system?).

Thanks for reading and any comments.
Cheers

 

[kzimmerman]

More cover in the pond will be extremely helpful, it will allow the feeder fish to have room for their fry to hide. Plus it will help the yellow perch to be more comfortable. You also get more biological filter the more you add. My small pond collects a lot of leaves, and I've never noticed a problem with them. Your going to have a problem keeping the leaves out of your bottom drain though.

 

[NetMax]

More cover in the pond will be extremely helpful, it will allow the feeder fish to have room for their fry to hide. Plus it will help the yellow perch to be more comfortable. You also get more biological filter the more you add. My small pond collects a lot of leaves, and I've never noticed a problem with them. Your going to have a problem keeping the leaves out of your bottom drain though.

Thanks for the feedback. Currently I've settled on Fathead Minnows (Pimephales promelas) as my prey colony, and will be constructing a barrier between the planted spawning zone and deep end (to hold the substrate & leaf litter) and I'm looking at pond skimmer designs to best capture the leaves in the deep end before they drop to clog the sieve guarding the bottom drain. My hesitation/concern with using too much organic cover is I don't know enough about organic-based alkalinity (especially which the seasonal cold) and the decomposition may consume my source of carbonates (old concrete, crushed coral etc) to cause a pH crash. I'm leaning towards sourcing pond 'mud' which will have depleted it's nitrogen content, instead of organic potting soil. Not detailed above, I'm planning biocenosis baskets to keep the NO3 down, but if I have too much ammonia (from decomposition), I'd expect the fractured clay in the BCBs to saturate (possibly negating their efficacy reacting with the laterite). I'm well over my head with this project, which is where my projects usually start during the design stage. Cheers

 

[kzimmerman]

Well, leaf litter and some mud is an important part of that ecosystem. It allows the pond to develop a lot more biodiversity. I'm not saying to let your pond fill with leaves, but a couple inches on the bottom is a good thing. Leaves don't decompose that fast, but they do provide a tremendous amount of available area for de-nitrification. If you built a wire mesh cage that's pretty high, and put something like corrugated plastic on the bottom 2' or so will keep most of the leaves and mud out. Anchor with cinderblocks or something. Cinderblocks are good because they also provide more cover if laid on their side.

 

[andyroo]

My experience from norther Sask many years ago is/was that pH has huge seasonal shifts & the fish (incl. yellow perch) don't (seem to) skip a beat. I suggest you not worry too too much about it, just make sure there's not too much top-end stock, some plants & plenty of water flow. Start with & follow what the koi people say to do as those things are yucky-messy, and from there think-through your trophic levels. Perch are lovely & colourful & nice, but so might be pumpkinseed, bowfin or sturgeon as time goes on.

Jaebos (DC) submerged should be well cheaper to run than 1-horse AC, particularly if the sum/bog filtration's not fighting head nor back-pressure. The bog will err your system acidic, pH <7, even before leaves & mud. Don't bother with mud per se as it'll come with the plants & bog, then as the leaves break-down. Look into scuds/amphipods & snails & tubifex(?) to accelerate leaf breakdown & sediments development. Also crayfish, which should also augment perch diet (and flavour). I might also suggest FW clams once the system's going, but take care you're not shifting protected or invasive species. To this & generally, try to control what species you add (including accidentally) as you can't get stuff back out again once it's established - leaches, for example.

If you put a perforated elevator pipe onto your bottom-drain intake then you will be able to keep a few inches of sediments in-pond, which the fish & plants (etc) will appreciate even if it looks a little naff & might impact bathing quality. That pipe will also reduce how often leaves (etc) clog that drain.

I don't know much about minnow spawning rates, but I'd expect they'll be seasonal, no? Will that be adequate to your perch-feed-needs? An good thing about perch is that they're generalists, so will be onto the hellgrammites & tadpoles & bugs & beasties as well as the minnows.

Our SCUBA photos are pending, yes?

 

[NetMax]

My experience from norther Sask many years ago is/was that pH has huge seasonal shifts & the fish (incl. yellow perch) don't (seem to) skip a beat. I suggest you not worry too too much about it, just make sure there's not too much top-end stock, some plants & plenty of water flow. Start with & follow what the koi people say to do as those things are yucky-messy, and from there think-through your trophic levels. Perch are lovely & colourful & nice, but so might be pumpkinseed, bowfin or sturgeon as time goes on.

Jaebos (DC) submerged should be well cheaper to run than 1-horse AC, particularly if the sum/bog filtration's not fighting head nor back-pressure. The bog will err your system acidic, pH <7, even before leaves & mud. Don't bother with mud per se as it'll come with the plants & bog, then as the leaves break-down. Look into scuds/amphipods & snails & tubifex(?) to accelerate leaf breakdown & sediments development. Also crayfish, which should also augment perch diet (and flavour). I might also suggest FW clams once the system's going, but take care you're not shifting protected or invasive species. To this & generally, try to control what species you add (including accidentally) as you can't get stuff back out again once it's established - leaches, for example.

If you put a perforated elevator pipe onto your bottom-drain intake then you will be able to keep a few inches of sediments in-pond, which the fish & plants (etc) will appreciate even if it looks a little naff & might impact bathing quality. That pipe will also reduce how often leaves (etc) clog that drain.

I don't know much about minnow spawning rates, but I'd expect they'll be seasonal, no? Will that be adequate to your perch-feed-needs? An good thing about perch is that they're generalists, so will be onto the hellgrammites & tadpoles & bugs & beasties as well as the minnows.

Our SCUBA photos are pending, yes?

Thanks for the feedback, much appreciated. For a clean look, I'm considering using a couple of IBC totes with media instead of the bog filter, as these can be tucked behind my deck. To manage the bottom drain, I was going to take a page out of aquarium filtration methods, and sandwich matt or sponge media, between two 4'x8' stainless steel mesh screens, to create a large void above the drain. It's the matten filter technique, where the rate of organics dissolving in the media is higher than the rate of detritus accumulation. This will provide a good home for various plankton, and the high level of dissolved organics will flow to the IBCs for further reduction. This will result in high nitrates, to be managed by aquatic plants and a diversion to some aquaponic gardens. At least that's the working plan. If I'm unable to keep the majority of the inevitable leaf litter/mulm on the upper 5K spawning bed, then I'll need to periodically vacuum the top of the matten filter. I'd love some Pumpkinseed sunfish, but it's only 20K total, so I'm thinking of keeping it to the two species for balance. The Fathead minnows spawn regularly throughout the season, and I'll give them a year head start before adding the Perch.

 

[jjohnwm]

Interesting project, I'm glad that it's still alive and in the works. I question whether or not the sort of balanced system you seek is possible in that size pond; as aquariums go, it's big...but as a pond to establish the predator-prey dynamic you want it's still very small. Fatheads are among the easiest to breed fish in the hobby, but they spawn during the warmer months of the year. They survive very handily under ice, but spawning shuts down completely during the cold winter months. Perch, on the other hand, are still very actively feeding under the ice (they are an ice-fishing staple) and will continue to reduce the numbers of the Fatheads year-round; I can't help but think that those Fatheads will be more of a put-and-take proposition as opposed to a self-propagating food source that persists throughout the year.

I think you will find...and I believe you mentioned this as well...that supplemental feeding will be required. In fact, I think that the feeding you do will be the primary food source, and the Fatheads will be the supplement to that diet. This might not produce the natural system you aim for, but considering that Fatheads are apparently a high-thiaminase food and that there will be no other fish species for the Perch to eat, it might be a good thing.

I am curious what basis you have for referring to Perch as filter feeders; I've never heard this before and can't see how it's possible. Perch are "panfish"...but they are still phenomenal predators that exhibit advanced hunting behaviours. As fry, they feed upon zooplankton...but it's still a predator-prey hunting life-style, as opposed to just randomly cruising around with their mouths open hoping to suck up enough zooplankton to get by. I have also found that they are tougher to get onto prepared foods than many other more generalized feeders like sunfish, etc. I would be heavily leaning towards doing this project with Bluegills or, better yet, Pumpkinseeds. They are generally easier to keep and feed than Perch, and the Pumpkinseeds in particular will be more visible and easier to enjoy.

Your Matten/prefilter idea sounds interesting, but I would suggest you plan for easy and fairly frequent cleaning as it will clog very quickly in a pond-type setting like this. Maybe set it up to allow vacuuming its surface with some sort of swimming-pool-cleaner device? You will start your pond by shovelling in some natural muck and leaves, but I'd wager that will be the last time you do so; after that, you will be amazed at how much of this stuff you will be shovelling out as it accumulates, both from your aquatic plantings and also from terrestrial leaves simply blowing into the pond. Someone needs to do a study regarding the tendency for every leaf on every tree within 100 yards of a backyard pond to miraculously migrate into the pond itself.

Two final thoughts that may or may not be worth bearing in mind: First, if you have dogs, it might be prudent to limit their access to the pond. A dog I owned once...the best dog I ever owned, as they all are ...enjoyed playing in the pond, resulting in huge messes and, in one case, the dog breaking through the early-season ice and splashing and floundering around in a terrified fashion; that was a scary incident for all of us.

And second: deer. Deer are a constant presence in our rural yard, and they utilize the pond as an easy water source during dry periods. Several years ago a deer managed to fall in, jump in, wade in, whatever...and in her increasingly panicky efforts to escape she tore the pond up pretty well, necessitating almost complete draining to repair a couple of nice holes her sharp little hooves put into the liner. Not fun.

Good luck with this project, looking forward to progress reports.

 

[NetMax]

Interesting project, I'm glad that it's still alive and in the works. I question whether or not the sort of balanced system you seek is possible in that size pond; as aquariums go, it's big...but as a pond to establish the predator-prey dynamic you want it's still very small. Fatheads are among the easiest to breed fish in the hobby, but they spawn during the warmer months of the year. They survive very handily under ice, but spawning shuts down completely during the cold winter months. Perch, on the other hand, are still very actively feeding under the ice (they are an ice-fishing staple) and will continue to reduce the numbers of the Fatheads year-round; I can't help but think that those Fatheads will be more of a put-and-take proposition as opposed to a self-propagating food source that persists throughout the year.

I think you will find...and I believe you mentioned this as well...that supplemental feeding will be required. In fact, I think that the feeding you do will be the primary food source, and the Fatheads will be the supplement to that diet. This might not produce the natural system you aim for, but considering that Fatheads are apparently a high-thiaminase food and that there will be no other fish species for the Perch to eat, it might be a good thing.

I am curious what basis you have for referring to Perch as filter feeders; I've never heard this before and can't see how it's possible. Perch are "panfish"...but they are still phenomenal predators that exhibit advanced hunting behaviours. As fry, they feed upon zooplankton...but it's still a predator-prey hunting life-style, as opposed to just randomly cruising around with their mouths open hoping to suck up enough zooplankton to get by. I have also found that they are tougher to get onto prepared foods than many other more generalized feeders like sunfish, etc. I would be heavily leaning towards doing this project with Bluegills or, better yet, Pumpkinseeds. They are generally easier to keep and feed than Perch, and the Pumpkinseeds in particular will be more visible and easier to enjoy.

Your Matten/prefilter idea sounds interesting, but I would suggest you plan for easy and fairly frequent cleaning as it will clog very quickly in a pond-type setting like this. Maybe set it up to allow vacuuming its surface with some sort of swimming-pool-cleaner device? You will start your pond by shovelling in some natural muck and leaves, but I'd wager that will be the last time you do so; after that, you will be amazed at how much of this stuff you will be shovelling out as it accumulates, both from your aquatic plantings and also from terrestrial leaves simply blowing into the pond. Someone needs to do a study regarding the tendency for every leaf on every tree within 100 yards of a backyard pond to miraculously migrate into the pond itself.

Two final thoughts that may or may not be worth bearing in mind: First, if you have dogs, it might be prudent to limit their access to the pond. A dog I owned once...the best dog I ever owned, as they all are ...enjoyed playing in the pond, resulting in huge messes and, in one case, the dog breaking through the early-season ice and splashing and floundering around in a terrified fashion; that was a scary incident for all of us.

And second: deer. Deer are a constant presence in our rural yard, and they utilize the pond as an easy water source during dry periods. Several years ago a deer managed to fall in, jump in, wade in, whatever...and in her increasingly panicky efforts to escape she tore the pond up pretty well, necessitating almost complete draining to repair a couple of nice holes her sharp little hooves put into the liner. Not fun.

Good luck with this project, looking forward to progress reports.

Excellent info. While researching the Yellow Perch, an author mentioned they were filter-feeders, but I'm quite sceptical as well. Perhaps it came from their bottom feeding habits and 'filtering' for zooplankton. No deer or dogs, and the fence will limit access to racoons, rodents and birdlife (I have regular visits from a pair of Mallards). The fence borders manicured parkland. It may happen that I'll need to culture some minnows every winter, and I do expect difficulties in keeping the Perch well fed. My plan was to seed from natural waterways and use depleted pond mud, to give the zooplankton a year's start while I sort out the filtration and plants. Hopefully any piscine pathogens will die off from the lack of hosts. I'll use the pond for some organic vegetation composting to keep things developing. Then introduce the minnows, and a year later, the Perch. The 5K spawning bed will be a collection of milk crates, plastic pallets and clay flue liner for shelter. If I'm a victim of my own success, Perch are better on the BBQ than Sunfish. Minimal deciduous trees in the area, as I've been watching the accumulation on the pool cover for a couple of years. I've no doubt, things will not go exactly to plan, but I'll research and build methodically, and deal with it (part of the fun is the fine tuning). My expectations for the matten filter are modest. It'll depend how successful I am at keeping the natural characteristic of the 5K side from the 15K deep end. I'll add a concrete berm with some kind of a connection to allow fish to go back & forth, but limit the muck at the bottom or surface coming over. This part alone sounds like a fool's errand, but we only live once to pursue silly things of our amusement. Thanks for the feedback, and I'll post progress, boringly over many years though.