Grow Media for Aquaponics!
No Dirt Needed....well, kinda
I have to be honest..when my husband first started this aquaponics journey with a fish tank and a plastic tub in the office I thought he was a little crazy. “Will the plants really grow without soil?” ”Is this really going to work?” But sure enough that little pepper plant we started grew a cute little pepper! It worked! Then I had to do the whole..”honey, you were rrrrrrrriiiiiiiigggghhhtttt”. He loves it when that happens! It actually happens quite often...but we won't tell him that;).
Come to find out this soil-less planting has been used for centuries, even as far back as the Aztecs (14th-16th century). The idea of soil-less gardening originated from Hydroponics. Aquaponics is just a combination of hydroponics (the soil-less growing of plants) and aquaculture (raising fish) in one circular system. The media environment of an aquaponics system has the same properties found in soil and is able to completely replace it. I said “kinda” above due to the fact you can start your seeds in soil, then clean off the soil and transplant them to the system.
There are several different types of grow media you can use with lots of reason to use or not use them. Some of the most popular ones are expanded clay pebbles, expanded shale, lava rock, and river gravel or pea gravel. It's not so much the type being the most important in making your decisions but the characteristic of the media. Media must be pH neutral to not change the pH of the system, not contain any other contaminates, be able to drain well so roots don't get flooded, well-sized to allow oxygen to get into grow bed (too small you get clogged, too big won’t allow plant roots to properly establish themselves due to the large air pockets created from big media), not decompose and be the right size for the good bacteria (nitrifying bacteria) to do their job (media with high surface area works best for this). A good size media is about ½ inch to 3/4inch.
With the mini office experiment we learned some things we like and some things we didn't so much like with type of grow media used. We, I say we, but really this was my husband's baby. My husband used expanded clay. He liked it because it was easy to handle. However, he said, “all in all I didn’t like it”. He said that it was so light and floated to where it acted like it was “breathing” and shifted the container and the contents inside. Also, the little rocks would get sucked down through the bell siphon. I think it’s safe to say he wasn’t a fan!
Fast forward from the mini office experiment to our 40ft by 80ft greenhouse with 12, 48 square foot grow beds and we really had to figure out what we were going to use that didn’t cost an arm and a leg! And the final decision was…lava rock!! I’d like to say we made the best decision ever and are perfectly happy with the lava rock, but that’s not the case. There are definitely pros and cons to it as well. We’ll start with positive! We went with lava rock first, because it was cheap! Well, relatively speaking, compared to what expanded clay would have cost us (buying in bags from Amazon or buying from a rock quarry for 12, 144 cubic foot grow beds???) Second, because it is because it is pH neutral and wouldn’t change the pH of our system-which is a very good thing! Especially when initializing the system! Lava rock also comes in different sizes. We decided to go with the ¾ size. However, when the rocks arrived there were quite a few larger than ¾ inch. So far it doesn’t seem to be too much of an issue though.
Cons..very hard to work with! It’s sharp so you need gloves (but you really should be wearing gloves anyway when dealing with fish poo, and especially with sharp rock due to the fact you don’t want to get cut and potentially contaminate you and/or the system). With a circular system it’s very important not to introduce anything unwanted because it is not going to go away easily! One thing we didn't realize we were adding to the system with lava rock is dirt! There was so much dirt that we believed is what caused the initial high pH of our system. However, I couldn't imagine washing the amount of rock we had in our system, but it is definitely something to consider! Also, due to the size of our rock it is more difficult for some of the small starts to get going. I’m not sure about how the red wiggly worms like it. Seems like it would be a little sharp for them but they seems to be alive and well in there! I’m probably worrying for no reason (per usual:)), but what can I say? I want the little worms to be happy in their home!
With future systems I would love to go with expanded shale; however, is does seems to be more expensive. For now we are going to continue to learn and grow:) with our lava rock! I cannot wait for spring to see what this lava rock is made of! I’ll give it a little slack with these seriously cold temps, it’s not able to live up to its full potential yet!
“For in the day of trouble He will keep me safe in His dwelling; He will hide me in the shelter of His tabernacle and set me high upon a rock. Then my head will be exalted above the enemies who surround me; at His tabernacle will I sacrifice with shouts of joy; I will sing and make music to the lord” (Psalm 27 5-6).
Scripture for though...1 peter 4-12