Backyard Aquaponics
A place to discuss aquaponics

Hi. I wanted to know if anyone has done an ebb and flow aquaponic system using Rockwool Blocks and Hydroton as the medium. I have tomatoes, Peppers, Strawberries, and cucumbers already growing in 6 in rockwool blocks. I wanted to put those in my tray and then fill it with hydroton and grow leafy greens in the hydroton. Any opinions would be greatly appreciated. Thanks

Rockwool might tend to stay too wet but I expect that it might be worth a try anyway. Let us know how it goes. I've never used the stuff myself.

Tend to think TCL is probably right... there have been peoplem that have tried coir and abandoned it for the same reasons.... although it might be possible to alter your flood & drain cycles to compensate... but then you affect your filtration and oxygenation...

Many rockwool and coir systems are "drip fed" in hydroponics... for the same reason...

So with the rockwool staying too wet you think I have a chance for root rot? How often do you typically flood and drain with AP?

Yep... typically we flood and drain with a 15 min on / 45 min off cycle...

From my experience with coir... I needed to adapt this to more like 15/180.... or even just twice a day...

Your climate might dictate more frequent cycles...

But IMO... hydroton is the better way to go...

Thanks. I live in Costa Rica so it is really humid and about 85 degrees all year around. I have used rockwool with an ebb flow system before and would flood it 3 times per day. My concern is that enough for the fish? I have a 2000 liter fish pond and a 700 liter grow bed. I guess from what I'm reading it will depend on the amount of fish. What would a safe amount of fish to start with?

The problem would be in acheiving sufficient water turnover... hence filtration, and oxygenation for your fish...

And we normally suggest turning over the volume of your fish tank once per hour.... i.e in your case 2000L/hr...

A 700L growbed wouldn't be enough on it's own to service your fish tank... at suggested stocking levels...

You could stock very lightly... and provide supplementary aeration.... but I still think you'd need to flood and drain at least 15/45 in your climate....

Three times a day... just wont hack it IMO.... seriously, I'd swap to hydroton and go for 15/45..

Even then, with only 700L of filtration (normally we'd suggest 2000L).... I don't think you'd be able to stock more than about 30 fish.... depending on species... I assume you'll be looking at Tilapia or Pacu??

So if I want to have a 2000L tank I should ad another Bed or make make my current bed deeper. The part that isn't calculating for me is if you have a 2000L tank and 2000L grow bed wont the fish run out of water? Thanks for helping to understand this.

Your growbed might be 1000ltrs but the media will displace 40%+

If you have 2000 liters of fish tank, you can easily have 2000 liters of grow bed and the fish tank will likely only fluctuate by 40%.

If you wanted 2000 liters of fish tank and 4000 liters of grow bed, you would then probably need to add a sump tank to deal with the water level fluctuations.

So I'm going to go with the Ebb and Flow. 2000 liter fish tank with 1250 Liter grow bed. I will ad some extra aeration to my fish tank and start with 30 fish. I'm going to use the rockwool but just for the starts and fill the tank with hydroton or a volcanic rock that they have here in Costa Rica that people use for hydro. As soon as I get this up I will share some pictures the goal is this weekend is to have everything built and running. Thanks for all your help and look forward to more help.

The volcanic rock would probably be fine for growbed media... just put some in a bucket and soak it for a day or two.... and check the pH level...