Backyard Aquaponics
A place to discuss aquaponics

I don't think it is. From the options I've looked at its not really cheaper either.

But using wood and liner makes sense if you're building a research tank that will need to be torn down eventually. Or may need to be remade in a more optimum shape.

One question I've always wondered about is if you have an IBC and you're trying to create a swirl, are you better off with one inlet at the side of the tank, or is it better to divide that inlet and have a second on the opposite side of the tank, what about split it four ways and have one on each side?

I should have been more specific. Using wood and liners the way they have done doesn't make sense.

There are some excellent quality liners out there that are almost as durable and puncture resistant as a poly tank. They are expensive but no way near as expensive as other options for large tanks. Because they are so good relative to their cost pretty much all large AQ operations use them.

On the other hand plywood and pine not such a good idea. Ply wood is expensive and not durable. Pine is cheap but so prone to rot that it is not cost effective. Bear in mind however, that those photos are from America and they have a range of pine species some of which are more durable than others. Personally though I would have used Calfornian Redwood, Monterey Cypress, Swamp Cypress or some other durable soft wood. Durable hardwoods tend to be too expensive and those softwoods will last for decades (plural ie 20+years).

Short answer is the side drains don't do much of anything to create the rotating current.

The speed of rotation is due to how much kinetic energy is being added to the water. Essentially you have a spinning wheel are you are using the jets of the inlets to make it spin.

I've noticed my fish are a bit like humans they like to expend the least amount of energy sometimes. When my fish aren't playing or engaging in other activities, I've noticed they like to sit with their bodies resting lightly on the bottom of the tank. Mostly they gather not moving anything just letting the current in the tank wash over their gills. They may have their mouths open, I can't tell, but it's definitely doesn't appear like a behavior due to some type of stress.

My tank water movement is a swirl that seems just the right speed for them to sit there without using any energy. This is purely by chance not by anything I designed into the system but it led me to think that I would avoid too vigorous a current in the future as the fish seem to like it.

I was watching River Monster( a tv program on dangerously giant freshwater fish) and in many of the underwater shots you see the wild fish exhibiting the same behavior, laying still with their bodies resting gently on a rock surface letting the water flow over their gills using the least amount of energy possible.

If fish like to behave this way, then it makes sense to mimic those conditions in our created aquatic environment.

Not talking about drains.

I'm talking about as you mentioned in your opening post, having a center drain/ SLO and an inlet on the side creating the swirl. Is it better to split your inlet in 2, one on either side, or leave it as one inlet.

Stuart, can you please expand on what you meant by... "Second you need a drain in the center of your tank. You can put this through the bottom or you can have it coming in from the top (I'll take some photos of mine tomorrow if people want to see them."

I take it this is different to common practice of having pipe with slits across bottom and SLO up side. Do you suggest the same concept but the vertical pipe being in the centre?

Sarah went to Bendigo with the camera so I haven't been able to take any photos. I'll knock up some drawings instead.

I've done drawings of two different center drains one from above and one from below.





Put a pipe through the center of the tank floor with a uniseal. Get a short section of larger pipe with one end capped and on the other end a flange. When I say flange I don't mean the expensive coupling flanges but rather (since we are talking BYAP) a PVC wall flange. These are just little pvc skirts that are meant to slip of pipes to cover up the hole in the plaster or tiles when a pipe goes through a wall.

Then from a piece of flat plastic cut a skirt in a donut shape that you then bolt to the wall flange with stainless steel bolts or screws. The heads of the bolts hold the assembly off the floor of the tank by a "bit" and that bit allows the waste to go through in to the drain but not the fish.

The eye bolt in the cap is in case you need to remove the cover you don't need to get into the tank. A broom handle with a hook in the end can be used to remove and place the cap if it ever needs a clean.

This option is not the best but it is an easy way to retrofit a tank. This is what I've got in mine.





Similar arrangement with the wall flange and bolted on skirt but it runs into a pipe, up and through the wall of the tank.

Both of these setups need an external standpipe so that the flow can be adjusted and the FT doesn't get inadvertently drained.

I felt this information should be included in the thread but I apologize for the distraction from the information Stuart is providing. It's a link to an article by Timmons reviewing circular tank technology circa 1998 -

http://www.extension.org/mediawiki/files/1/1e/Review_of_circular_tank_technology_and_management.pdf

There's also a slide show that has more but related information and photos - http://ag.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/4%20Culture%20Tank%20Design/Culture%20Tank%20Design.pdf

Carry on

What keeps the center drain cover from getting kicked around?

Stuart, with the flange cap eye bolt setup , do fish ever knock the cap off? Seems to be nothing holding it to the tank floor, or does the pipe protrude up from the ground floor through the uni seal enough to hold it there combined with the weight of cap and ss bolts?

Stuart,

This is awesome information. Thanks a million for taking the time to write it.

For a typical IBC, would it be recommended to build / place a sparger in all four corners, or would one be sufficient?

Also, would it be a good idea to inject air into the spargers to make up for the lesser amount of DO without having the water fall into the tank?

Looks like its time for me to set up a few experiments.