Backyard Aquaponics
A place to discuss aquaponics

I've looked through the feedback on grow bed media and couldn't see anything relating to damage to grow bed liners from the media.
Is the liner on a corrugated iron tank tough enough to take gravel being poured in/cleaned out many times?

I am not sure about your question, I would think it may be better to wash the gravel in a smaller container instead of risking damage to the lining.

Really I am just curious about the engine photo. I see its a V-12 of sorts. What is it?

From the Rolls Royce heritage website...
"Crecy – V12, 90°, sleeve-valve, liquid cooled, 26.1 litre, supercharged, two-stroke, mechanical fuel injection (from Focke Wolf 190) Otto-engine. The 1942 prototype had surprisingly low fuel consumption at the highest power output. In December of 1945, after eight years of development, work on the Crecy was terminated. At that time the Crecy was capable of double the horsepower of conventional 4-stroke designs of the same displacement. Only six Crecy engines were built, all with even serial numbers (2, 4, 6, 8, 10 and 12). This has led to confusion as to the numbers made. Crecy engine #10, achieved the highest test horsepower in December 1944, putting out the equivalent of 5,000 brake horsepower."

The last statement is incorrect (I have a book co-written by several of the engineers involved in the project), the V twin testbed engine achieved ~200 bhp/litre, which in a main engine (26L) would be over 5000 bhp.

What kind of gravel are you thinking of using?

I haven't tried but I would say defiantly don't use any gravel that's rough or sharp in any way or you'll end up with leaks everywhere. The rounded pea or river gravel might be OK but I'm not sure.

Thats freakin incredible about the engine. Do any exist today? Have you ever seen one? You would think a two stroke would have worse fuel consumption. Is this the engine used in a P-51 Mustang?

Sorry I am off topic.

Oh yea just make you put clean gravel in your tank and you will be fine.

No, it never reached production due to persistent sleeve failures - most of the engineers attribute this to feeble oil pump volume on the main engines (with 20-20 hindsight).
P-51's initially used an Allison V-1710 (60 degree 1710 cubic inch), later replaced by a Rolls Royce or Packard built Merlin (again, 60 deg V-12, but 1650 c.i.) due to higher power.
The fuel economy is due to the stratified charge mechanism, basically no fuel is injected until the exhaust port is closed.

Getting back on topic, I have spoken to a tank manufacturer and despite a 5 year guarantee I am going to put expanded clay on the bottom and sides (held with some plastic sheet) and fill in the rest with a local gravel just to be sure.

UY, you wont have to clean the gravel once it is in the growbeds - people have been going for over 2 years with no signs of getting blocked growbeds, just give the gravel a clean first and pour it in.

If growbeds are to sit in the same spot for a lengthy time or permanent, would it not be alright to make them out of ferro concrete and do away with all the worry? It's cheap, not affected by the sun, durable and could be poured on a simple mold with pipe fittings in place. My brain hurts from concepting a mold all week

I'd have to check that out as we have fairly reactive clay soils round here, some kind of expansion mechanism would need to be incorporated. Also, the c.i. tanks don't need to be destroyed if you want to move them later.

you can get some super tough liners. the better ones are so tough you can't push a steak knife through them, so i think gravel is going to be ok.

I'm using the 45 mil EPDM firestone pond liner. It is tough stuff though you can cut it with a knife if you are actually trying to (be hard to put fittings through if you couldn't.)

Anyway, my fish tank is lined with the stuff but there isn't gravel in there.

My Grow beds are also lined with it. The beds themselves are made of wood and lined with the liner. I washed my media before placing it in the bed. I was not particularly gentle about how I put the media into the bed and I have dug into the beds with hand trowels to plant seedlings. My media is not especially smooth or at least half of it is not. My media is a mixture of 1/2" river rock (kinda smooth) and washed shells, lots of sharp and rough though brittle bits. My system is new but no leaks in the liner yet.

I also built a pond about 8 years ago that uses that same kind of pond liner. The liner has stood up to rocks shifting on it with concrete under it over the years and no leaks there either.

I don't know about the particular liner or coating on the tank you are talking about though.

There should be no reason to repeatedly remove and wash gravel as the maturity of the bio slime in the gravel bed is a good thing so washing it off is a bad thing.