Backyard Aquaponics
A place to discuss aquaponics

Just curious, what is it about the cypress mulch that is bad for the fish. I probably wouldn't want to use anything so temporary for a AP system anyway but I'm interested in the details.

Cypress pine has chemicals in it that exclude the growth of other plants. I can't recall which ones they are right now, but search on here for cypress, I typed up a heap of stuff about it ages ago.

As far as I know I can't get Hydrotron (clay balls) but I do have an expanded clay product available. It seems smaller that Hydrotron (3 to 6mm, 1/8 to 1/4 inch), all manner of shapes. It is not bagged and is about $40(US) per yard (a little less than a meter sq), so it's not terribly expensive. And it does have a some dust, but it's not bad. The use of this stuff is mostly for concrete overhead structures because it's about half the weight of limestone gravel (the whole state of Tennessee made of limestone).

There seems to be two possible objections to using this.

1) It is small and "will have poor root aeration". If this is true, how true is it? I mean, is this a real draw back? If I have water with lots of dissolved oxygen, will it make any difference?

2) About 5 to 10% of it floats after soaking a while. Will this floating actually be a problem. Or does it just look strange? One fellow on the Aquaponics list suggested that it would tare or rough up the roots. I dunno.

Thanks,

Jim

RupertofOZ, doing metric isn't so bad after all.

What are the clay balls called?

I have been growing in 3/8 inch pea gravel for two years now. No crop has ever had a problem with that size.

I am using 1/4" gravel as well, plants haven't complained about it yet.

The reason something floating would tear up plant roots is only if the floating is a large section of the media. Like you flood the bed and everything starts to float up, the plants don't get much stability in such a situation where their whole ground shifts on an hourly basis. If it is only a few bits that float until they manage to get waterlogged, it should be ok.

The drawback I've found with smaller media is that water doesn't move through it as fast as in larger media. This is only a real drawback if you are trying to use large siphons. A way to get around this issue is to put larger gravel (I used lava rock) around the standpipe area for the siphon to allow faster drainage into the standpipe to keep the siphon from sucking air too soon.

If the clay bits are of a shape and nature that they will tend to pack down, it could be difficult for the plants and you to penetrate. You might get a bucket of it if you can and see how much it tends to pack and how difficult it is to dig into for planting and stuff.

I've been using a mixture of washed shell and 1/2" river rock. The washed shell seems to be keeping my pH at 7.6. It is a little rough on the hands for planting and will probably tend to break down over time and the media in the bed will slowly loose volume but I'm hoping that I will be moving in a couple of years so this could actually be a good thing. The washed shell is lighter weight than the river rock but it requires more washing. Even after washing, adding it to the system will cause very cloudy water for a time (the amount of time depends on the amount of filtration already in the system and the maturity of the rest of the system. The more bio-slime, the quicker water clears.)

Dave, Dan & TC, thanks for the comments. I feel relieved.


They just call it expanded clay. No brand name. Looks like rough gravel; multi -colored, but much lighter. I got it from a contractor supply (General Shale) that sells brick and block. They mix it in concrete in overhead structures. And landscapers use it for mulch. This was made in Memphis Tennessee. hard to believe it's unique to here.

If the floating part is any sort of a problem (there is less now than when I first posted; maybe it will all sink), I think I could just skim it off the top and discard it.

Jim

Jim,

The tendency in these systems is to have the water come up to 1" below the top of the grow media. Unless the whole thing floats, I don't think you'd have a problem. I have a combination of expanded clay (the larger type) and pea gravel that ranges in size from very small to about 3/8". The bed drains fine and I still have some hydroton floating around here and there. I just pick it out of the water and drop it on top of my grow beds. And, my plants are growing well.. though the system is only about 1.5 months old.

I know this idea has been bandied about a little bit, but I have some questions about the use of styrene foam peanuts for a growbed media. I'm not planning on having growbeds more like large PVC pipes with the media packed inside and plants growing from holes on top., so floating media isn't a problem. Weight and cost however are problems. Gravel is too heavy, and expanded clay is too expensive.

Anyone have any thoughts on foam peanuts? I figure they are super light, super cheap, chemically nuetral, should drain well and readily available. My worste fear is that they would leach nasty stuff into things I want to eat. I havn't found any evidence of this in my research however.

There is also a large semi-commercial hydropic garden close to me that grows lots of lettuce and tomatoes. Interestingly, the lettuce is grown in corrugated plastic roofing, with just a small amount of foam to anchor the roots and a continuous flow of water flowing through the troughs formed by the corrugations. Tomotaoes are grown in long tubular bags filled with what appears to be vermiculite.

Hi strangetanks, I had exact same thoughts regarding the foam peanut shells.....

I wasn't convinced as to the ultimate safety regarding any possible leaching... many differing opinions regarding polystyrene....

I did actually trial a barrel full as I was build ing my growbeds but found two major problems...

One, if the wind comes up it blows them everywhere...

Two they float.... big time...... tried weighing them down with other stuff like coco chips, hydroton etc and ultimately gravel....

Found that only a layer of gravel would in any way work.... even then the gravel wanted to sink and displace the shells and with a couple of flood and drains, and attempts to transplant seedlings it became almost impossible to work with the stuff......

If you went a mix of say 50:50 shells and gravel/clay balls ... maybe....

Personally I consign it to the shelf ... right alongside the perlite

Be OK to run in a drum as a bio-filter though... like bead balls.

As far as im aware hydroton is about twice that cost at $35 for 50L, 1000/50=20, 20x$35 = $700 - who was the supplier that you found vb?

hehehehe...I went back several pages and couldn't find the vb quote water bender - think you might find that the scoria quote is over 2 years old mate

found it...1 Sep 2006

lol nevermind trying to get it cheap, its simply not available here. ive spent all morning looking and have come up with nothing