Backyard Aquaponics
A place to discuss aquaponics

Can any one tell me if it a definate advantage to put sumps or fish tanks in the ground for temp stability? I know OBO and F&F have theirs in the ground but I wonder if the air temp affects the water temps when cycling throught the growbeds to make the advantage a waste of time? Does have temp of the air feeding the air pump help with water temps. eg in summer put the air pump in the fridge or something - will that bring the water temp down?

I currently have 1000 IBC in green house and although keeps warmer in the winter I seem to get large fluctualtions in tmeps and would like to minimize that as much as possible so I was going to drop 1 or 2 IBC in the ground to replace my sump similar to Food & Fish and use them as fish tanks as well.

Another question to Rupe or anyone else using 90mm PVC pipe to grow plants in. I was thinking if incorparating a length of 90mm into the system flood and drain with separate pots with their own media (small river pebbles or something) and inserting into a 70mm hole on the top of 90mm pipe similar to what I think I have seen by either Rupe or somone who has numerous rows using this method I think. Even though it is not the recommended 300mm depth of media to enable bateria to grow effectivily will this method work ok as I seem to have seen here before.

Any thoughts on that anyone??

Altron, I use standard hydro trays... and NFT... not flood & drain...

TCL uses 90mm, with net pots filled with gravel (from memory).... but I'm not sure if she uses flood & drain or nft..

Hi if thinking of running nft you will need clean water i use water after its been though the grow beds

For temp control you have to have fish tank sump and grow beds bury ed [ ie just a grow bed out in the elements will eather heat or cool the water 1 or 2 deg in one pass]

Excuse my ignorance but what exactly is NFT ?

I was going to cycle water from my FT through the 90mm and use old round seedling containers with small river pebbles just in the container and not the pipe. Does that work?

F&F how much have you stablized your temps with your system. Are you saying that if you had one bed in a hothouse it would mess up the whole system temp? I am using baths with a white looking river pebbles into 1 IBC

Not same as NFI altron, but check out this link for all BYAP acronyms viewtopic.php?f=14&t=1275

Yes nft nutrient film techniques [ah la a film of water passing the root zome ] as for temp every thing has to be buryed or it dont work OBO has his fish tanks and grow beda buryed and there is a difference I am shore he will chime in soon and give more details

My FT is buried.

Hi alltron,

without a doubt soil temps are more stable than air temps.

I believe that burying your sump and fish tank [much as practical] will help even out temp swings that can kill your fish.

Where I live sub soil temps help keep my systems water cooler in summer and warmer in winter.

God bless froggo.

The ground might help keep temperatures more even, but at a lower overall temperature. Winter ground temperatures are cold and will cool water down so I dissagree a little on the buried tank. I buried my sump so I could do CHIFT PIST but I insulated the sump to stop the cold winter ground from chilling the water. (pictures in the link below).

Instead of burying the tank I kept the it above ground and put the system inside a greenhouse. The thermal mass of the whole system contained in this way meant that my water temps stayed higher than a previous sytem that had the tank buried.

And I in turn disagree with you It is very dependent on your climate.

In summer my ground temp is cooler than my air temp, yes.

In winter my ground temp is warmer than the air temp.

My 90 mm pipes are running as NFT pretty much thought the water in them is a bit more than just a film. My NFT pipes are not really part of my filtration, they are using water that has flowed through two levels of flood and drain gravel beds. They are more as a way to grow lettuce efficiently if the weather ever cools down enough for it.

Temperatures and using geo or ground exchange to help with system temperatures. I'm in a sub tropical climate. It can get cold enough for a freeze to damage a citrus crop here but the ground never really gets too cold. Putting tanks in ground here has a benefit even with my grow beds being out of the ground. However, on really cold nights even in the greenhouse, the air infiltration into the gravel will still chill the water enough that I had to use supplemental heat to keep the tilapia healthy over a cold week with multiple freeze nights in a row.

So, if you are in a climate/location where your ground temperatures are good for the type of fish you wish to grow (if your ground temps are lower or higher than desired, then don't bother or use insulation around in ground tanks) then digging stuff into the ground can be a great benefit temperature wise. However, flood and drain media beds make really efficient temperature exchange devices with the air so additional measure will likely need to be taken if trying to keep tropical fish warm over winter or trying to keep cold water fish cool over summer.

Don't know if this really answered your question very well. In my location, sinking stuff in the ground is worth it but the grow beds still have a drastic effect on temperature. Without the tank in the ground, I expect the fluctuations would have been too much for my tilapia last winter and I would have been bankrupt by the electric bill too.

Pretty much the same here, though probably not to the extremes of Kalgoorlie.

Ground temps here in winter are similar to the air temps (maybe slightly warmer), however by capturing the heat during the day and containing it within the greenhouse I have had a better result than burying tanks.

The critical thing was putting the system into a greenhouse and having good thermal covers on top of the fish tank for winter warmth.

For summer heat shade cloth over the whole system and lifting the lids up off the tanks keeps the heat down.

I insulated my system including the growbeds, it's about 1700L including the sump, and I use scoria which has some insulation capacity. I find that my temps vary about 2-3c per day 3-5c on the hottest summer days. I also have a buried 1000L tank and that sits at about 2-3c below my aboveground tank. The buried tank is to change water only during the hottest part of the day, I can pull the system down by about 1.5c.

In my area the daily variation is about 10c with 17c in summer and about 25c on the hottest days. So in the hottest day last year we went from about 19c to 47c the tank went from 21c to 26c (I did not have the underground tank then).

With my experiences so far I think a buried sump, a partially buried tank insulated above ground and insulated growbeds would probably work more effectively than what I have.