I am considering installing an aquaponics element to my garden and or greenhouse. I am pondering what kind of growing medium I should use. I like the idea of using very small gravel/very large sand because of the more natural root growth and distribution. Then I thought about the possiblity of using straw, either entirely or chopped and mixed in with some small gravel. What do you think?
One problem I was thinking of is the fact that straw is organic and will break down, but it can be changed out after every crop.
1. It will cause clogging problems. With... virtually every component in the plumbing. Pump, drain, bell syphon if you use it, etc. etc.
2. It will suck up the nitrates and other minerals you are attempting to get into the water.
For gravel/media size I have seen many systems have issues with gravel that is less than 3/8" inches in diameter. Most clogging/dead zone issues. You want the water to flow freely and remain oxygenated/aerobic. Anaerobic conditions cause bad/wrong bacteria colonies to form. They grow/spread MUCH faster than the good bacteria. They also SMELL. A good running system never smells bad. The also REVERSE the nitrification process... killing the fish.
Be sure that whatever you use it is solid and PH neutral! Look up "Vinegar test". I have had Great luck with scoria/volcanic/lava rock. Hard to find in smaller size (I just use the larger ones). They have Excellent mineral content (that breaks down to feed the plants over time), surface area, and lock together to give the plants something solid to hold onto. Not to mention the large voids between the rocks than enable great water flow over time.
Let me know if you have any further questions and I might be able to point you in the right direction.