Backyard Aquaponics
A place to discuss aquaponics

Hello everyone. I have been browsing information about aquaponics for the last few weeks now and have finally decided to build my own. I wanted one small enough to keep in the house during the winter so that it would not take up much space. I've decided to use a 60 liter Rubbermaid for the fish tank but am now running into trouble finding a grow bed. I've read that one should have a 1:1 ratio between tank and grow bed. I have found a 55 liter Rubbermaid to use for the grow bed and am wondering if that will be too small for my 60 liter tank.

A 2:1 ratio is recommended... a 1:1 ratio will put your close to the edge of your filtration capacity, unless you stock accordingly...

Depending on how nice you want it to look you could get a blue barrel and cut it in half. Many people use those and they're not too big.

old bath tub ?

If you can manage to have close to equal amount of grow bed and fish tank and then stock less fish you should be ok. And with only 60 liters, you are not going to be growing out edible size fish so some nice small goldfish should be fine.

In larger systems where people want to grow as much fish as possible, having twice as much grow bed and fish tank is recommended but then you need some means of sequencing the flooding of the grow beds or you need a sump tank to handle the water level fluctuations. Or else you need to run constant flood so there wont' be water level fluctuations.

Okay thanks!

Now that I have decided to go with a 120 liter grow bed, I can't figure out what size pump to use. I plan on having half of the water being drawn out of the tank pumped right back into the tank for aeration. I was thinking around a 140-170 GPH pump.

You sequencer sellers..... I tend to go the opposite way, 1:2 ratio is beautiful....

I'm going this way too on my first build because of how I acquired my supplies. I ended up grabbing a 60 gallon tank from craigslist because it was so darn cheap. $25US. I have a 20 gallon concrete mixing tub as my grow bed.. so that is a 1:3 ratio GB: FT. I am worried that the plants will not filter the water enough because the ratio is so off. To fix this would I just use less fish? or maybe not fill the tank full with water?

I'm glad you chimed in on this ratio thing EB. Seriously gave me massive drama in the beginning of my system trying to get to the right ratio. Then I saw your posts regarding 1:2 ratio systems and I quit sweating about it.

Basically somewhere between 1:2 and 2:1 is fine. Just stock to the size of your grow beds, not your fish tank.

What would 55L of grow beds give you, 3 pounds of fish?

Thats the winner Native.... It's really just not about the ratio of fish tank to growbed at all... And I can;t stress that enough... I have a great system here at home, my oldest system still running, about 8-9 years old and it has almost 4000L of fish tank to a growbed that I think is only about 200L... Been running a treat....

I've got three systems of 1.1:1, 0.75:1 and 1.5:1 and the first system has produced two lots of edible fish, the others are on hold for future reports but I reckon they will do ok
Now my brain hurts

This whole ratio thing had me confused and it still does. But then I realised there are no hard and fast rules (just some very important and key principles) . Anyhow it got me thinking about the stocking rate and volume of grow bed. Correct me if I have this wrong but the ratio is about filtering capacity. if this is correct would a constant flow system have a greater filtering capacity for a given sized grow bed than say a 15:45 min on off cycle due to the greater amount of water that is passing through the filter medium (ie grow bed gravel)? If this is correct should we not take this into account as well?

Therefore if a system was heavily stocked (or if the temps were up and feed significantly increased) would running the grow beds on constant flooded or even a 15min on and 15 min off cycle help to deal with the increased ammonia better than the traditional ebb and flow (15mins on and 45 off). Or have I got this totally wrong?
Cheers
Marc

The BYAP trials indicate that there's not any real difference between running constant flood, and flood & drain... in terms of nitrification....

But the fact remains that if you haven't got enough filtration capacity for your stocking amd feed rates... then it probably wont matter which system you run anyway.... you'd still be under-filtered....

Yes, the truth is you have to find a balance. One of the problems comes when people set up a system and then stock the max amount of fish their fish tank can handle with little concern for the amount of filtration they have. If you are going to stock max fish for your fish tank capacity (without needing oxygen injection) then you need the 2:1 Grow Bed-Fish tank ratio and a sump tank or means of sequencing.

If you are going to be sane about your stocking and grow your fish according to the amount of grow bed you have, then the other ratios work to a point.

I Have seen situations where people take an entire swimming pool and hook it up to a single little grow bed and wonder why the system is struggling when they only stocked the appropriate amount of fish for the grow bed. (But there is no way to filter all the water from the whole pool through that poor little grow bed each day let alone each hour without spraying all the media right out of the bed so the pool still becomes green and turgid.) This situation often also comes along with trying to save money over using the pool pump so the pump now in use is only able to handle moving an appropriate amount of water for that one little grow bed and really isn't able to filter the whole pool.

Anyway, for a simple starter system with little other information the 1:1 ratio is generally good provided stocking is according to the amount of grow bed and not the full fish tank. Same goes for the 1:2 grow bed to fish tank situation however the larger the fish tank, the harder it seems to restrain people from putting too many fish for the filter. I hate seeing those IBC with top 6 inches turned into grow bed since so many people still try to stock the IBC as if it were a 1000 liter fish tank with all the filtration necessary to stock to the hilt!!!!! Well I only stocked it with 100 fish why are they dieing?