Polyculture Within Aquaponics

[cncventure]

I'm not sure if anyone has brought this up before (no doubt they have) but I was wondering do many people add anything like redclaw, marron or yabbies into their fish tanks to act as detritivorous feeders?

If so do you offer them a bit of protection maybe a small mesh/netted off area so the fish don't hassle them too much?

Also would adding a cm or two or sand or gravel to a small section of the fish tank for the crayfish to rustle around in be OK?

[Mr. Mik]

I have not quite managed to understand why the vast majority of AP systems run an animal monoculture. Probably mostly because it's tricky to keep different species (or the same!) from eating each other. That is perceived as a "loss" when fingerlings are being bought on a regular basis.

But, if one chooses species that breed in the system, then it does not matter so much if a large part of the population ends up being eaten by other animals in the system.

This is largely theoretical for me so far, or rather in the very early stages of being tried out. I'm keeping Redcalws, Pacific Blue-eyes, Yellow eel-tailed catfish, Plecostomus and White Cloud Mountain Minnows together.
So far, I've found a few dead Redclaws and one dead Pleco with a hole in it's abdomen (might be from a Redclaw attack, before or after it died).

Apart from the Catfish they should all be able to breed in the system (1000l FT, 4 small and one large sump). The Catfish **might** possibly breed in one of my larger rainwater tanks - maybe I'll throw in some gravel one day when they have reached maturity and look like they are ready to breed. Apparently they build a 1m diameter gravel bed for spawning.

For the Redclaws and Catfish I hope to soon add multiple bamboo-tube hiding places. So far, they have a piece of PVC pipe each, but many of them are open on both ends and I don't think that's good. They can get attacked from behind that way.
Did you see the link to the intensive Yabbie farming system yesterday? http://www.blueyabby.com/edu-video
IMO as bad as intensive chicken farming, but effectively keeping them from eating each other. Maybe someone will come up with "de-clawing" as a method - maybe I just have..... I have used one of the small sumps as the "hospital sump" when I got the first lot of Redclaws. All those with less than two claws were put in there, about 7 or 8. They seem to be doing well. Need to count and compare....

I'll soon need to get into the gender identification and separation for the redclaws, apparently they fight less and grow better if kept in separate male/female tanks.

For gravel on the tank bottom I'm still pondering options. I intend to make some sort of frame out of bamboo culms. Maybe a few large diameter culms at the bottom, then smaller and smaller diameter towards the top of a pyramid shape or wedge shaped structure. Like a coral reef, with an above water platform so the crayfish can get to the insects landing on the water without climbing out of the tank.The large diameter at the bottom could keep a space for gravel open and protect it from being thrown around continuously by larger fish. There could also be some secure anker points for aquatic plants in the structure.
The bamboo might not last very long under water, but *might* be a food source for the crayfish. They seem to like some gumtree leaves that have blown into the tank.

[RupertofOZ]

Mr Mik... your approach seems to be to replicate an aquaria style of polyculture...

That's fine as long as you're prepared to adopt the necessary regular water changes, and gravel cleaning practices....

But if you don't.... the gravel will become a depository for all the wastes from the redclaw, fish and uneaten feed... which will ultimately lead to a stinking anaerobic mess... and potential fish kills....

Most Australian native fish will not breed in RAS style systems... without hormone stimulation... the eel-tailed catfish might... if all the planets align... but doubtful...

This is why most people run monoculture systems in AP.... reduces potential problems and the necessity for excessive maintanence...

[Murray]

Multiculturalism has not yet come to the fish world. In nature fish eat other fish and they protect themselves by hanging around in "schools" or with their own kind. It is a bit hard to replicate in a tank and things go better if you keep only one species in a tank.
Some "cousins" get on ok, such as Jade and Silver Perch together in one tank, and some "odd couple" relationships like Ell tailed catfish and Silver or Jade perch. I am not sure even that would work too well if a couple of catfish got big and decided to mate.....:)

[Mr. Mik]

Mr Mik... your approach seems to be to replicate an aquaria style of polyculture...

That's fine as long as you're prepared to adopt the necessary regular water changes, and gravel cleaning practices....

Why should this make water changes necessary? I was unknowingly running a sort of an AP system over 30 years ago: A 300l aquarium with relatively few fish and lots of plants. All I did was top up the water, add little amounts of fish food and harvest water plants for sale on a regular basis. I barely ever did water changes in that tank (unlike the other 30 tanks that I was looking after). It was the same principle as an AP system, just harvesting water plants instead of salad greens....it had a 60-70mm gravel bed that remained relatively undisturbed for many years, due to the absence of large fish.


But if you don't.... the gravel will become a depository for all the wastes from the redclaw, fish and uneaten feed... which will ultimately lead to a stinking anaerobic mess... and potential fish kills....
I think any gravel layer in the FT needs to be thin (or absent), so that no dead spots can develop. That's the best part of the crustaceans behaviour: They continuously dig around for any leftover food. Without over-feeding, there will be no build-up of waste in the tank.


Most Australian native fish will not breed in RAS style systems... without hormone stimulation... the eel-tailed catfish might... if all the planets align... but doubtful...
They probably refuse to breed in an environment that offers no plants, caves, gravel etc to allow a chance for the offspring to survive. With enough hormones you might still force some of them to breed....


This is why most people run monoculture systems in AP.... reduces potential problems and the necessity for excessive maintanence... Just like in farming - but mono-cultures bring their own problems with them, for example an increased risk of catastrophic total loss of the entire harvest.



Multiculturalism has not yet come to the fish world. In nature fish eat other fish and they protect themselves by hanging around in "schools" or with their own kind. It is a bit hard to replicate in a tank and things go better if you keep only one species in a tank.

As long as they keep eating each other, they are eating and growing....until they are big enough for the biggest "fish" in the system -me! I don't expect them to get along nicely - and not in just one FT only. I'll interfere by re-locating them to one of the 6 separate tanks/sumps that I have in the system from time to time. I might also put a separating mesh into the main tank, to keep large predators away from some areas.

Anyway, you guys might well be right and in a year or two I admit that it's too hard - but for now I remain unconvinced that monoculture is the best way to go.

In the worst case I'll just be running an ugly aquarium (without water changes) that produces veggies on the side....but no edible fish or crustaceans. :carrot:

Mik

[fishman]

I also have a fish tank (natural plant system) where i dont do water changes.I even have 50mm of clay under the gravel.In this system as opposed to ap the plants are rooted in the gravel and by doing so move water though the bed reducing the chance of stagnation as well as removing nutrients.
This does not work in the bottom of the fish tank in ap as there are no plants to do the above nor light to grow the plants.