Backyard Aquaponics
A place to discuss aquaponics

A little history first...

I have a 29 gallon aquarium with tropical fish in it. It is using a power filter for mechanical filtration (no carbon, just filter media) and a skimmer (again, no carbon, just filter media). In my first setup, I used an under gravel power head to pull water through the gravel then above the aquarium to a single 4” PVC tube with several 2” net pots filled with hydroton. It worked ok so I moved on to my current setup, three PVC tubes running in parallel. Again, it is running ok. Although in each setup, the plants grow “weird”, as in the lettuce and cabbage don’t grow in heads, but off of stalks or branches...

Anyway, it takes up a lot of space and I am thinking of changing to tubs with either rafts or filled with hydroton.

I like the hydroton because I can either start the seeds in another area, or just in the media. It also seems like bigger plants could have more support with deep roots.

The rafts seem appealing because they appear to be simpler to work with and the extra water volume would buffer any changes in the system.

What are your thoughts? I’ve been mostly just trying out things on my own so any advice would be appreciated.

It sounds like either one would work. With the rafts you would have to provide support for larger plants if you want to grow them. You might also need to provide additional filtration for fine solids, although your pipe setup doesn't need them so your system will probably be OK without.

Using media does provide better support but is a pain if you're going to have to move the system.

You could do a combination of media and raft to see which you like the best since you don't have to be tied to one or the other.

Yep, I like that idea. I’ll run a second under gravel power head and just alternate fill times between the two.

Thanks!

You could also run the system using Constant Flood. Basically design the grow beds so that the water won't drain back to the tank if the power gets shut down and have the pump run 24/7 so that the continual movement aerates the water (you can probably get away with aerating at night without operating the water pump if it bugs you but it's better if it's always on or on most of the time). A standpipe in each grow bed keeps the water level at the correct height (this is surrounded by a media guard). This way you can keep the fish tank full all the time and don't have to be concerned with water level fluctuations.

It's very difficult to keep grow bed fill and drain synchronized if you're using siphons (eventually they'll trigger or fill together). If you use timers and separate pumps or some sort of switch (I forget the name of these but they fill grow beds in sequence) it can be done but don't rely on water flow to trigger the switch to get the synchronization.

Actually, that's what I was thinking of doing, I just didn't know it had a name associated to it.

My plan (as of now) is to have two beds, 1 raft and 1 hydroton. I'll have pump A timed to run for 15 minutes to the raft side, then shut off for 15 minutes, then pump B would run to the hydroton side for 15 minutes, then shut off for 15 minutes, and repeat that cycle.

I figured each tray would have a drain a few inches from the bottom so there was always some water in it and the aquarium volume wouldn't change too much.

Like I said, I've been doing this mostly as trial and error so far. But any tweaks to this idea would be helpful.

That sounds like it will work. A couple of suggestions -

1. Don't glue any of the fittings within the grow beds. This allows you to access them for cleaning and also allows you to swap out the standpipe if you need to change the water depth.

2. For media beds I think it works best to install the standpipe with it coming up through the bottom of the container. It allows you more water depth adjustment range within the container. It also makes cutting the media guard a bit easier to cut.

DWC beds are done differently - I think it's typically through the side on the end of the bed so that the outflow doesn't obstruct the placement of the rafts. You should try to find some information online about this - I'm sure there is plenty out there or someone may help you here. I have 14.5 ft long DWC channels with a bottom drain and standpipe arrangement - some of my rafts are suspended over the channel and don't float so the standpipe isn't really an issue for me but probably will be for your setup.