Do I need bottom drains?

[Meyer Jordan]

but I still think ammonia levels would go through the roof if you had visibly accumulation levels on the bottom of the pond.

Not really. The Ammonia that is released by organic decay is gradual and is usually assimilated by the existing algae or oxidized by the Nitrifying bacteria present throughout the pond. If Ammonia levels approach the assimilatory limits of the pond, Nature steps in and provides a solution....an algae bloom. This would be very similar to the processes that take place in the Spring.

 

[sissy]

true because when you feed fish you are feeding a pond .My plan all along was only 8 fish but pick maybe 1 or 2 each year to see what happened as they grow and if I did not like how they looked I gave them away .Right now I have a couple that want 8 of my babies but they may have to wait .Thing is a lot of people do not think there will be babies and start out over stocked and as time goes by it gets worse .Seems goldfish just love making babies .

 

[Mucky_Waters]

Not really. The Ammonia that is released by organic decay is gradual and is usually assimilated by the existing algae or oxidized by the Nitrifying bacteria present throughout the pond. If Ammonia levels approach the assimilatory limits of the pond, Nature steps in and provides a solution....an algae bloom. This would be very similar to the processes that take place in the Spring.

Well, I don't know, I've never dumped enough fish food in my pond at one time to try that out. What I do know is that it would take a heck of a lot of fish food to cause the kind of muck and mulm levels I've seen in seen in peoples ponds or ever seen in my settling tank. In fact, it would take more fish food than I normally ever keep on hand.

 

[MitchM]

Part of what constitutes "mulm" is bacteria colonization of suspended and dissolved organic matter. Once enough bacteria has grouped together, that grouping of bacteria will sink down to the pond floor and accumulate.
That's why water circulation is so important; circulation that transports the mulm to a filter of some sort or circulation that can keep the mulm in suspension until it is broken down further by bacteria and taken up as a plant nutrient.

 

[Mucky_Waters]

Obviously, circulation is important but most ponds (without bottom drains) have poor water circulation in their lower regions, a sort of a dead zone near the bottom where the suspended "mulm" is able to settle out. Typically, a thin layer of this stuff is not harmful, in fact, some would argue that it is even beneficial because of the bacteria colonies you speak of. However, if it gets thick enough the lower levels can turn anoxic which is generally considered an undesirable condition is a backyard pond because of the type of bacteria that grow in those conditions and the type of gas they produce (H2S).
To be sure, this is a common condition in many natural ponds and even many backyard ponds where they can exist for years with this anoxic layer of biological activity going on in the bottom of the pond, providing it is relatively minor and/or does not get disturbed. Disturbing, or stirring up a thick layer of this stuff in a pond with fish in it would result in a quick release of toxic H2S that would be harmful, if not lethal, to the fish.
This layer of muck is a very common condition in many ponds, in fact, there is quite an industry built around the removal of this undesirable layer of pond muck.

Somehow I doubt that all that muck in the above ponds is the product of excess fish food.

I prefer to rely on my bottom drain and settling tank for removing the muck from the bottom of my pond

 

[brokensword]

Obviously, circulation is important but most ponds (without bottom drains) have poor water circulation in their lower regions, a sort of a dead zone near the bottom where the suspended "mulm" is able to settle out.

Somehow I doubt that all that muck in the above ponds is caused by excess fish food.

I prefer to rely on my bottom drain and settling tank for removing the muck from the bottom of my pond

Well, I can say there's not a lot of 'dead' area in my pond as with a submersible pump on one end (on the bottom) and a stream + waterfall on the other, there's definitely flow toward it. I've had no need for any extra plumbing and associated bottom drain at all. I think you're only going to get a buildup if the balance is off, whether it be by dissolving plant organics, fish excrement, or uneven food. Been 7 years now and I have a full pond of plants, 100 fish, with no rock bottom (or skimmer, or settling tank--just a mech filter and bog), and the only thing there is clay/soil that's been spilled from the lily pots over time. Now, the natural pond at the end of the road here has quite the deep mulm layer. And I doubt it's from anything but an overabundance of decaying plant matter.

 

[Mucky_Waters]

Having a submersible pump at the lowest part of your pond will certainly help with circulation and exactly what I did in my last pond to help with keeping the muck off the bottom, but many people will avoid doing that because, as you are probably aware, it is advised placing your pump up on a shelf or something off the bottom of your pond to avoid draining your pond completely if you happen to spring a leak somewhere in your external plumbing.
So there's that to consider.
Also, many pond designs only have a skimmer as the sole mechanism for water return in their pond filtration system. Certainly, this type of pond would have a "dead zone" near the bottom.

 

[MitchM]

Obviously, circulation is important but most ponds (without bottom drains) have poor water circulation in their lower regions, a sort of a dead zone near the bottom where the suspended "mulm" is able to settle out. Typically, a thin layer of this stuff is not harmful, in fact, some would argue that it is even beneficial because of the bacteria colonies you speak of. However, if it gets thick enough the lower levels can turn anoxic which is generally considered an undesirable condition is a backyard pond because of the type of bacteria that grow in those conditions and the type of gas they produce (H2S).
To be sure, this is a common condition in many natural ponds and even many backyard ponds where they can exist for years with this anoxic layer of biological activity going on in the bottom of the pond, providing it is relatively minor and/or does not get disturbed. Disturbing, or stirring up a thick layer of this stuff in a pond with fish in it would result in a quick release of toxic H2S that would be harmful, if not lethal, to the fish.
This layer of muck is a very common condition in many ponds, in fact, there is quite an industry built around the removal of this undesirable layer of pond muck.

Somehow I doubt that all that muck in the above ponds is excess fish food.

I prefer to rely on my bottom drain and settling tank for removing the muck from the bottom of my pond

Right, I was responding to your comment about the relatively large amount of mulm you see vs what can be attributed from the addition of fish food or decaying plants.
As to the OP's question, a bottom drain isn't needed, but is an effective way of dealing with decaying organic matter. Otherwise, sufficient water circulation and filtration or a substrate with submerged plants are other ways to prevent water quality problems in the pond.

 

[brokensword]

Having a submersible pump at the lowest part of your pond will certainly help with circulation and exactly what I did in my last pond to help with keeping the muck off the bottom, but many people will avoid doing that because, as you are probably aware, it is advised placing your pump up on a shelf or something off the bottom of your pond to avoid draining your pond completely if you happen to spring a leak somewhere in your external plumbing.
So there's that to consider.
Also, many pond designs only have a skimmer as the sole mechanism for water return in their pond filtration system. Certainly, this type of pond would have a "dead zone" near the bottom.

True, dat, but I also employ a float switch to guard against just such an event.

 

[Mucky_Waters]

a bottom drain isn't needed, but is an effective way of dealing with decaying organic matter.

Interestingly though, by far the majority of ponds with bottom drain systems are dedicated koi ponds that have no aquatic plants and primarily use their bottom drains to deal with koi wastes (poop). I find this a bit odd from an old aquarium keeper's point of view, as I use to have some fairly heavily stocked aquariums, which of course never had bottom drain systems, and never found poop accumulations to be significant. Generally, any fish poop would quickly disappear or dissolve into the water and be dealt with by the filter system. Granted, my aquariums probably had much better water circulation than the average backyard pond.

 

[MitchM]

Interestingly though, by far the majority if ponds with bottom drain systems are dedicated koi ponds that have no aquatic plants and primarily use their bottom drains to deal with koi wastes (poop). I find this a bit odd from an old aquarium keeper's point of view, as I use to have some fairly heavily stocked aquariums, which of course never had bottom drain systems, and never found poop accumulations to be significant. Generally, any fish poop would quickly disappear or dissolve into the water and be dealt with by the filter system. Granted, my aquariums probably had much better water circulation than the average backyard pond.

A lot of people vacuum the gravel substrate plus do water changes with freshwater aquariums, whatever it takes to get rid of the poop. You can't really do that on an outdoor pond. Plus an outdoor pond has atmospheric dust being blown into it as well. That dust could be topsoil (organic material) or clay (mineral plus phosphate absorbent material), depending on where you live.
I had pretty good success with my Walstead type aquarium. Always interesting stuff.

 

[Meyer Jordan]

Part of what constitutes "mulm" is bacteria colonization of suspended and dissolved organic matter.

This is true. Bacterial floc (as it is called) can constitute a large percentage of the apparent sediment at the bottom of a pond. And here is where fish food comes into play.
Fish food is typically 20% - 30% carbohydrates (sugars), the food of preference for heterotrophic bacteria, and much of this is passed trough the fish undigested to become part of any sediment. Because bacteria prefer sugar as a carbon source (easier to oxidize), colonies will rapidly form to devour this nutrient bounty. The drawback to this is that as long as this sugar source is available (and it is usually added daily in fish feedings) the other organic debris is largely ignored, being acted upon only by fungi. This allows it to accumulate in various stages of decay often to dangerous levels in poorly designed ponds as @Mucky_Waters mentioned.
Sediment, whether from fish food, externally sourced organic debris or other sources, is a naturally occurring on-going event. Its accumulation can be controlled by an adequate water flow pattern that will either transport it to a mechanical filter and/or a settlement chamber (sump) where it can be removed and discarded.
This water flow pattern can be imparted without the use of a bottom drain even in those ponds that utilize peripherally mounted skimmer units.

 

[Mucky_Waters]

That may be part of the difference - I remove all dead lily pads, faded blossoms and any other dead or dying plant matter. And the algae is handled by the fish. They are like a landscaping crew, keeping the algae clipped close to the rocks. And maybe that's because they aren't overfed - they have to work for some of their food. When people say "remove any food your fish don't eat in X amount of minutes" I'm like "huh?" We feed in small amounts at a time, making sure every morsel is gone before we toss in more. We kind of have to - the current will carry any food out and over the edge before they can eat it if we feed too much at a time. And we stop long before they are full. But once the food stops falling from the sky, the grazing starts. We say they are like the French, eating their salad after their main course!

Well, I must have extremely finicky or lazy fish because I also feed limited amounts at a time making sure all the excess is eaten before offering them more, and it is not that unusual for them to get only 1 or zero feedings a day sometimes. However, I still get a significant amount of algae growth, so much so that I could probably use a rake to remove the algae like the guy in this picture is doing. My fish are totally ineffective and cleaning up my algae. The actual algae growth I get is on sides of the pond and the rocks along the shore where it gets plenty of sunlight. Like in the picture below it is long hair like algae that hangs and trails along in the water current, either towards the skimmer or towards the bottom of the pond. The longer ends tend to die and break off where it gets sucked up into my bottom drain and gets captured in my settling tank where I can easily remove it without disturbing the pond itself. Without the bottom drain and settling tank, it would end up simply accumulating at the bottom of the pond where it would start breaking down and turning into that thick layer of decaying organic matter that would be more difficult, and messy, to remove.

 

[brokensword]

have you ever tried NOT feeding them at all for a period of time? I bet if they get hungry enough, a lot of that algae will go missing...

I don't remember; does your pond have plants? I find a well planted pond also has less issues...

 

[Lisak1]

so much so that I could probably use a rake to remove the algae like the guy in this picture is doing

Well, that could be the difference right there. The only algae we get anymore is the "carpet" variety algae on the rocks. We get several different forms of it, but no string algae in the pond - some on the waterfall occasionally, but nothing to write home about. Early on, we had LOTS of string algae that I would remove with a rake. It would form big clumps in the bottom of the pond that were easy to catch and rake out.