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About thebloks

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    small scale development for South East Asian rice farmers

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  1. Sorry I haven't been back here for awhile. My system is still not up and running! Have had a few issues with getting washed sand and also a few other delays. Had to get some sand and wash it myself as no one in Thailand has ever heard of washed sand. Oh except the pool filter people, but they wanted 300 baht (US$10) for a 40kg bag. So we aren't going to use their sand... It took us about a week to wash the sand ourselves which wasn't much fun but it was mostly done by a local who I am paying. We have just put a roof on the grow bed today and I have the safety/screen doors coming down on Monday for the fish tank. So we should be able to fill the fish tank next week. We already have some catfish (15) and tilapia (~100) to put in. I take it mixing these is a bad idea?? I'm happy for the catfish to be sacrificed for the cause as they only cost me about US$4. The tilapia cost 500 Thai baht or about US$17. To answer VKN's questoin we started using a local Thai product on a concrete rain water catching tank and it hasn't worked well at all and water is still seeping out of it. So we are now using Flintkote which is made by Shell and is a black bitumen type of thing which dries into a waterproof layer. It was pretty expensive though ~1900 Thai Baht for 5 gallons. I've attached a photo of the grow bed with the Flintkote applied before the sand went in. And one of our new roof. You can see the grow bed with sand in it. We plan to build another inside the old shade house. Any comments are welcome!
  2. Hi all, I have started building an iAV system and have a few questions. Gary said I should ask them here so here I am. We live in Thailand and are doing development in some mountain villages. We are at 1000m above sea level which helps keep us a little cooler than the lowlands. I want to make a pilot iAV system at my place so our village friends can see how it works. They are very interested and love the idea of growing fish and veges together. I'm just not sure they will have the capital to get something like this set up. They earn about $10/day if they are out working for someone else. Anyway I plan to do this mostly at ground level. Thankfully our place is on a gentle slope so gravity will help. I haven't found anywhere that helps me with ideas for design of an iAV system (other than iavs.info). And the system that is modeled there is a little big with a tank that is 3.25m x 1.25m So I have a question or two. I have dug a hole in the ground that is 1.5m x 1.5m x 1.5m deep for the fish tank. I wanted it deep so that the water stays cooler in the hot season and warmer in the cold season. (It gets over 40 C in the hot season and down to around 5 C at the coldest). I plan to concrete the hole and then line the concrete with a sealant that will make it all water tight and stop the concrete affecting the pH of the water. I don't know where to find the true pond liners around here and I think they would be prohibitive price wise for our village friends if they are going to copy what I do. I also wanted to dig the hole before the rainy season starts as that would make it difficult to work in after monsoon rains come. They are late this year. We have a shade house just up above the fish hole/tank that will be where we put our sand grow beds. I haven't yet found sand suitable. The four sands that I tested didn't react to vinegar but failed the turbidity test taking days to come clear and having quite a layer of silt on top at the end. No one I have asked has any idea about washed sand. So I think this could be quite hard to find. The only thing that came close was sand that is used in swimming pool filters. But it is prohibitively expensive. ($10 / 50kg sack). Anyone washed their own sand? I think that will be crazy time consuming and maybe put our village friends off doing this. If we ran the system as a filter for a few weeks would the silt end up on top of the sand and we could scrap it off? Any other ideas for how to clean sand yourself would be very welcomed. I haven't made the grow beds yet but I am wondering about the size of them. Our shade house is 6m x 3m so its not that big and we want to be able to walk around the grow beds for access to pick produce. I think from my reading the area of the grow bed needs to be 6m2 for every m3 volume of the fish tank? So if our tanks are ~3.4 m3 then I think I need to make the grow bed(s) about 20m2. Please correct me if I'm wrong on that. I'm hoping that will be enough. Your thoughts would be appreciated. If I'm right then I need to build one or two inside and a similar amount outside. I'm also wondering about having a tank further up the hill that we grow duckweed in. That could serve dual purpose - getting the ammonia out which grows into food for the fish and settling some of the solids. I really don't like the idea of having to clean the sand in the future and I thought that this might be a way to avoid that while also growing duckweed. Have you done anything like duckweed with an iAV system? Not sure how long it will take to get this up and running but will keep you posted. Here are a few photos of the progress so far: You can see our shade house above the fish tank. Painting on sealant to keep the concrete from changing the pH of the water. Cheers! Greg
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