Backyard Aquaponics
A place to discuss aquaponics

Dear everybody,

First of let me start with introducing myself, my name is Quirijn and I'm new to aquaponics. Never owned a system before and am dying to start. However after reading a lot I still have some questions (probably newbie questions though).

1. My first requirement would be, that the system would be usefull to have, so for question number one:
What size would be required for a system to actually feed you? (square feet/inches/meters) Not in all your
needs but in adition to your regular groceries would be nice. I plan on growing only plants, no edible fish.
2. For a general rule of thumb the dept of your growbeds should be 10". However if not so (say a 5" high
container) are you still able to plant most beneficial plant species such as for instance tomatos?
3. What's a must have in your system? I really like an ebb and flow growbed, but what would you add?

I have some resources available such as 4 30 liter containers for growbeds, so my system could be (with wat i have) 120 liters of fishtank and 4 row's of growbeds. Would this be sufficient for an nice little indoor system?

Thanks already for the replies.

The official recommendation for grow bed depth is 12in but 10in will work fine if that is what you have. Mine are 11in so I mound up the media a little but tomatoes would be fine in a 10in bed.

The 12" depth recommended for grow bed gravel is more to do with ratio of fish, and therefore nutrients, per square meter of GB's.

From a stability point of view, shallower beds will work, tomatoes and larger plants can be supported, but the shallower the bed, the less fish you can stock per m2 of GB, so less nutrients... and if you half the GB depth it reduces the fish stocking capacity by more than half.

ie:

A 1m2 bed x 300mm gravel depth, flooded to 260mm (that's the level I use in my beds), gives the following amount of wet, or working gravel:

100 x 100 x 26cm = 260L... so a safe stocking capacity of 10x Trout (require 25L+ of wet gravel per fish), or 13x Silver Perch (require 20L+).

...if we then then half the gravel depth:

So a 1m2 bed x 150mm gravel depth, flooded to 110mm (same distance as before from surface), gives the following amount of wet, or working gravel:

100 x 100 x 11cm = 110L... so a safe stocking capacity of 4x Trout, or 5x Silver Perch.

So you can see how important gravel depth is... for example: If you were running Silver Perch, the 300mm deep gravel could support 13x fish... but at half the depth, the 150mm deep gravel could only support 5x Silver Perch... nearly 1/3 the amount of fish per m2 of GB... so only 1/3 the amount of nutrients.

Clear as mud?

Absolutely clear, very usefull information, thanks.

Applying math to what you say helps me wrap my head around this haha.
For what I've read so far is I should strive for that 1:1 ratio of GB to FT. Lets say I would use GB of 12cm high x 70cm lenght and 40 cm width, resulting in a 33L GB. If I would use 8 of those I also have 260 liters of growbed meaning 13x trout fish poop in the water. However I will have 8 x 70cm x 40 cm = 2,24 m2 of growbed but half the nutrients fed to the plants, yet I'm maintaining an ratio of 1:1 but not the recommended depth of 12" (sorry i thought 10"). It's not just because of the solids build up in your growbed that you want a 12"/30cm deep growbed but also because of the nutrients?
Forgive me for probably this newbie question but what are the limits of the m2 growbed per liters of water?

What would you recomend as an nice starter size system? (keeping in mind I would like to start indoors)

I'm not experienced enough to answer you properly.
Regarding the 1:1 ratio, you can easily have a greater volume of growbeds than of fish tanks.
There is no need to strive for 1:1, 2:1 or even more is fine (gb:ft).

And just a side note in case you didn't catch it - the 1:1 ratio is WET media to FT volume. You typically do no get the top inch or two wet to prevent algae growth. The wet media is your filter/bio-filter where the good stuff grows to convert the bad stuff (ammonia & nitrites) into nitrates.

Amount of wet gravel determines your systems ability to process ammonia into nitrate. This is of primary importance when discussing bed space. However, looking at only this, we would come to the conclusion that a very shallow but really long and wide bed would do the trick. This would be fine for the fish but a disaster for the plants.

You must consider the amount of space the roots will have when full grown. planting tomatoes in a 2in bed would not turn out well regardless of how wide or long the bed is.

Each plant is different is this regard. Stick as close to 12" as possible (10" is fine). There are a few golden rules in aquaponics and this is one. It does not mean you can't it just means proceed with caution.

Hope this is helpful.

Absolutely, with every answer I learn more new interesting facts. Using a 2:1 ratio would mean half the nutrients to the plants, in my opinion the fruiting plants such as tomato's will probably use a lot of nutrients to fully grow. Is there somewhat of an indication of the size of the root systems of the plants?

One question still remains, what would be an ideal size of m2 of GB?