I am a newbie trying to learn more about aquaponic. These are the little that I read up about media or raft:
OK, that's all I can think of. I am wondering if one can have a combo system?
Thanks for helping.
1 and 2 yes basically correct (though there are some very low stocking density raft systems without extra bio-fitlers.)
3) You might not have to buy a truck load of gravel but Remember that DWC requires the Rafts and the net pots and media for the net pots and can require extra work in starting seeds then putting them in the rafts.
4) for all systems you have to balance your fish load to your filtration capacity, this can be fairly easy if you keep your fish load small then a 1:1 media system works and if you want more fish you can go twice as much gravel as fish tank and add some means to deal with the water level fluctuations.
For Raft systems, you still need to make sure you have enough filtration for the fish load and then you can look to Friendlies or UVI numbers to figure out how much plant bed for a particular amount of fish feed. I don't know those numbers so well but my understanding is that 19 lb of tilapia can be supported in one of their micro systems that has a 300 gallon fish tank and 64 square feet of raft bed.
5) yes extra aeration to the raft beds is important for DWC. Here in the hot south, I recommend at lest some air pumping to the fish tank of any type of system in summer or some means of supplemental aeration because water staying very warm means limited dissolved oxygen and the fish will eat/grow better with ample dissolved oxygen.
6 and 7) As to when power out, DWC the raft bed doesn't drain so the plants have plenty of water, either one will keep the plants happy enough for a few hours. The fish are another story, if heavily stocked some means of battery backup aeration might be needed to keep them alive if the power is gonna be out for more than a few hours.
8) The rafts are good for some plants but most will also grow just fine in media and there are many plants that are far more suited to media. The main benefit of rafts in my experience is gonna be for commercial operations where being able to lift a raft out at one end for harvest then clean up take it to the other end and plant the seedling into the system.
Yes combo systems are possible and many people have lately been experimenting with having the fish tank water flow through media beds before going to the rafts to avoid the need for solids removal and separate bio-filtration.
I am designing an experimental system to get myself educated and involved. I am thinking to have a combo system, deeper media for plants like okra and some 18" deep channels for lettuce etc., I would like to try having shrimps in the channels, not sure if they need access to the surface as it will be mostly covered by raft. That way, I can experiment productivity.
What kind of shrimp?
I'm hopefully about to start growing some cherry shrimp (not big enough to be food for us) if I am successful enough with them, some may become food for catfish.
Good question! I saw lots of swimming fresh water shrimps or prawns in local Asian supermarket. Quite big, 2"+, some of them were loaded with eggs. I have no idea what they are but figure if I can just buy a few pound, quarantine them for a few weeks before releasing to the troughs. Then hope that they will multiply. Those are food shrimp, so pretty big.
I have purchased those shrimps and live crayfishes for my home aquarium. They lived for days, some even weeks but eventually all got eaten by predatory fishes. I have arowana and frontosas, both got big mouths.
My aquaponic is still in the planning stage ...