Backyard Aquaponics
A place to discuss aquaponics

Hello aquaponic’s friends, I’m Mike from Italy! Some weeks ago I’ve inherited a part of commercial aquaponic facility (who is under construction) because of the renunciation of a member who has had problems. The facility has been projected by this guy and we have lost all of the calculations and design with his leaving. I have some doubts about design of the system and I hope some of you can help me to solve these. So, first of all, media beds! We have a fish tank of about 2110 gal (8000 L), a mechanical filter+biofilter (both in the same tank), n.4 media beds and a DWC. We want to adopt a 2110 gph (8000 l/h) flow rate in order to recirculate fish tank’s water one time every hour. Thinking to use a flood-and-drain system in media beds, we have about 80 gal (300 L) of water for each media. This means a drain every 6-7 minutes (more or less) and I suppose this is a too fast cycle. I’m valuating also to use different methods like constant drain. Do someone have suggestions?

Hi Mike,

As per my reply on your other thread, in some situations and designs it's not essential to turn over the FT water volume through the GB's every hour.

A full description of the system, it's components, their layout and the intended operating method etc, would help. A system layout diagram would good too if you can provide one.

Also, how many fish are you intending to run, what type, and what size are you intending to get them too?

P.S. It would probably be a good idea to delete one of your two threads, just so there aren't two separate conversations taking place about the one topic.

Thank you so much for your reply Mr Damage!
Our facility is composed by n.2 identical systems. Fish tank (8000L), mechanical filter + bio filter (about 1200L), n.4 media beds, a DWC (about 60m2) and a Sump tank (1000L). I will try to upload later a schematic diagram to show you the layout of the system. We assume to use the rule of 10-20kg of fish each m3 of fish tank (totally about 120kg of fish). We’ll use koi carps and goldfish. We’ll start with an high density of young fish and we’ll balance the ratio during fish’s growth.
Let me know if you need further info to help me

Here a schematic layout.

So there are two pumps in this system, is that correct?... Has this system actually been built yet?... As I would change MANY aspects of the design, in fact I would start from scratch and redesign the entire system if you have the ability to do so.

What are the volumes/dimensions of your four media beds?... ie: L x W x Media depth. If you want to run the media beds as Siphoned F&D, as you've suggested (and I would recommend), then the flow rate through the media beds will be determined by the diameter of the standpipe in your siphon, which should be chosen after taking into consideration the volume of the GB's and exactly how you wish to operate the system.

As this is intended to be a commercial system, is there any reason why you are choosing to use non-edible fish instead of edibles that could provide a second income stream?... Also, depending on the type of plants you envisage growing, you might find that koi may not be suitable, as koi food doesn't have the same nutrient profile as commercial fish food used for farming edible fish, and if you feed koi the commercial type feed it is not good for their health due to the high protein levels.

Even just growing plants with low nutrient requirements such as lettuce, herbs etc, in the DWC, 60sqm will require a good deal of fish to provide sufficient nutrients for the plants, plus you need to take into account the plants in the media beds. So the media beds will need to have a sufficient wet gravel volume (bio-filtration) to sustain the number of fish required to provide nutrients for all plants in the system, ie: both the DWC and media beds, unless of course your external bio-filter has sufficient capacity to support enough fish when combined with the bio-filtration capacity of the media beds.

Also, I would have a separate mechanical filter (ie: Swirl filter, or Radial flow filter) to the external bio-filter. I would not have a combined unit. I would also run the system as a CHOP 2, or split flow, with multiple flow loops.

Yeah I think at this point some photos would also be useful in order to inspect particular elements of this system... how is the filtration unit constructed?

2 pumps is definitely not how its done... you should pump from the lowest part of the system to the highest, and let gravity move the water through the rest of the system. For this reason you need "solids lift overflow" (SLO) drains to suck the solid waste up off the bottom of the fish-tank and to the filter. Have you planned this? It doesn't look like it from the diagram...

You've got the components to build a great system here, and the people on this forum will be happy to point you in the right direction(s), but you must be patient, do research, and make sure you understand all of the the concepts involved in the design and build.

A badly designed system will quickly lead to problems, and will fail in the long run... ESPECIALLY if the intention is to go commercial!

At the moment, fish tank, filter, media beds, DWC and Sump tank are already constructed and installed. Piping system, drains and power units are missing.
Each media bed is 4.5m long, 0.33m wide and 0.26 height (internal dimensions).
About fish, we decide to choose koi mainly for following reasons:
1- Tilapia is not diffused in Italy and we think tilapia doesn’t represent a business here for what concerns food market.
2- We evaluated trout, but talking with biologist and some trout breeder here, we discover that trout required life parameters who needs high knowledge and huge investment.
3- koi is a long life fish and it has more larger tolerance in water parameter than trout.
4- we are considering also catfish

Filter is made with n.4 sectors: in the first brushes, in the second one “Japanese Mat” and in the third and fourth BioCarriers. Water flow from a sector to the other one by a forced flow (up&down) to increase and decrease its speed.

You could try running it this way and see how it goes but I agree that the setup is not ideal. I think you'll have to clean the filters enough that it will be a pain. For a commercial system, a bead filter would be easier to clean and probably a better choice. I would flush solids out of a bead filter to an aerobic mineralizer and then feed nutrients back to the grow beds as needed (excess will wind up growing algae if the tanks not shaded).

A drum filter might be even better since less water would exit the system.

Thank you for your feedback Danny. I’m with you about badly plant construction concept! As said in the first post, I’ve inherited the plant and now I’m trying to make the system as better as possibile but using components already built. This not means that I don’t want to make any modifications.. I write this post in order to collect feedbacks and info from persons who work with the aquaponic system longer than me.
So, I’ve upload a layout of the actual configuration and I ask to the community to tell me suggestions and feedbacks in order to complete/improve it.
Attached also some pic of the plant.

Cool, nice space you've got there!
That looks like some kind of baffle filter... How is bio-filtration incorporated? I imagine the lager section would contain a bio-media? This isn't conventional way of doing things; normally people use a radial flow filter (RFF). Have a look at some examples on other threads. It looks like it wouldn't be to hard to convert what you already have.

Also look at the solids lift overflow (SLO) this is how you want your water, with the solids, to flow from your tank into the filter, with gravity. Your fish-tanks and filter will need holes in the walls for pipework to be plumbed through the side.

Then the water would flow from the filter into the grow-beds, to the DWC and finally into the sump. The single pump would be located in the sump and would return the water to the fish-tank.

It would probably be better, as suggested by Mr Damage, to have seperate filtration units, i.e. turn the round container into swirl/rff and then have a separate biofilter / suspended solids filter, where water flows in an upward direction through a media, eg. gravel. If the fine suspended solids are not removed they will clog the roots in the DWC. As it stand your media beds will do this to an extent, but will eventually need cleaning as the fine solids build up, and that kind of maintenance work isn't what you want in a commercial project. Media growbeds in general are seldom used in commercial settings because its less practical... plants can't be moved around easily, digging up and planting takes time and energy, media gets everywhere.

Also, the sump is pretty low down. If it was a little higher, i.e. almost level with the DWC, you would reduce head height a bit, which could save a significant amount of energy in the long run.

Finally, in terms of fish, have you considered Zander, aka pike-perch? These fish grow more slowly than trout, but have a much wider temperature tolerance and I imagine they would grow pretty well in the kind of temps you'd have in a greenhouse in Italy. They are also very good eating, and as they are carnivorous their metabolic waste would be better for plant growth... more ammonia and less solid waste. I believe trout feed is appropriate for them, so should be easily available.

Scotty435 thank you for your feedback!
We have plan to substitute actual filters with bead filters or similar in some years as per reasons you have mentioned! About algae, our filters have a top cover in order to avoid algae growing.


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Yes, it is a baffle-filter concept, based on aquarium’s filters. Bio-filtration will be made by using BioCarriers. I know this isn’t a conventional way to do filters, and I agree with you about separate the two filtrations; but in this moment we have limited cash available and for this reason we’ll try to use this kind of filters. In any case, we’ve plan to substitute them in few years with bead filters or similars, for maintenance reasons first.
Fish tank has a grid on its bottom to receive all fish’s organic waste and by a pipe water flows to the filter. So water is taken from the bottom of the fish tank.
I agree with you also to Media bed is not recommended for commercial purposes but this is what old company’s member has built and designed. As said by you, it can be used mainly as per additional filtration.
You suggest to use only one pump located on sump tank and use gravity for flow water to other components of the system, correct? My issue is that between filter and last media-bed have a distance about 18m and I think pressure drop should be considered. But, first of all: starting to Media-bed volumes, how can I calculate water flow rate?

Finally, thank you for fish suggestion, that’s very interesting. I’ll investigate about Zander habitat or, if you have info/documentation yet, please could you share me?

I see your point about the difficulty of delivering water by gravity to all the grow beds; as they are in a row it will be difficult to achieve equal flow to each...

Mr. Damage suggested a multiple loop configuration, this could make things easier. You could have two pumps; one from sump to fish-tank and the other from sump to grow beds. Pumping to the grow beds would make even distribution easier to achieve as you mentioned. Multiple pumps should never be used in a single loop system, because they will inevitable go out of sync and over-flows will occur.

There is no reason the solids drain from the fish tank wouldn't work. However, the reason people use SLOs is because there is no risk of draining the fish tank in case of leaky plumbing, or mistakes or accidents. Component parts can also easily be removed for cleaning or replacement etc. What if there is a blockage? Will you be able to locate it and access the pipework to clear it out?.. I'm still not sure exactly how you're planning to configure it but anyhow, careful consideration must be given.

Here's a link to Zander info: http://www.fao.org/fishery/culturedspec ... ioperca/en

It looks like Slovenia is a producing country, so if you can't get the fingerlings in Italy, then perhaps you can get them from there. They require a low lipid diet, so sea bass feed would be better when they are bigger, and trout feed when they are still small.