Mangojohn, you/'ve pretty much identified most of the choices, with the exception of coir or conventional potting mix.

Perlite can be a pain in the net pots as it falls out. By the time the lettuce roots have become entwined in the perlite youwon't have much that can be reused for the next crop. If you can get good quality horticulutral coir that has had allof the salt leached from it, coir would be a good alternative.

Oasis foam cubes work well and you could probably dispense with the net pots, although you could just set them in the pots if you wish. One advantage of the Oasis foam is that youc an sell the lettuce with the cube attached as a "live" product. Cost can be an issue with Oasis.

One other alternative is to use a potting media (1/3 peat moss or coir, 1/3 perlite, 1/3 vermiculite) and start your plants in a 280 cell tray. These cells are tine, about 3/4" x 3/4". When it is time for transplant into the NFT system the roots will have contained the media and you can put the root ball into your system. Rice hulls have also been used for media in tropical countries.

If your going to go NFT you need to make provisions for pump interruptions. One way is to install a solenoid valve which is normally in the Off position when nutrient is flowing from your nutrient tank. If, for some reason this flow is interrupted then the solenoid trips to On and opens a valve which is connected to the outside water supply. The plants won't get nutrients during this time and the nutrient tank will get diluted and overflow with the influx of outside water, but the crop won't be lost.

Hi Adriana, I like the idea of the live products. I saw some lettuce in the market yesterday and their roots are still attached. Thats my reason for thinking of the sponge cubes in replacement for the oasis cubes. Oasis cubes are not available here. Would you know what the oasis cubes are made of, its possible that it is being sold here but with a different name.

Mangojon, Oasis is used by florists also. Check with them to see if they can get large absorbent foam cubes and see who makes the product which is avaialble locally.

Have you found a lettuce variety which will grow well in your heat?

Adriana, Is Oasis a brand? My wife is a wedding planner and she asked one of her florists about the foam. Florist says there are two type of foams, green for fresh flowers and brown for dried flower arrangements. But don't these floral foam crumble after a peroid of time?

We are experimenting on the lollo rosso or rossa and lollo bionda variety. Oak leaf red or green seems to be a little more resistan to heat compared to others. There are few more varieties here that are being sold but the names have been changed to indentify them with the seed supplier (green and red rapid). Mizuna is also being sold here, they may be imported from Australia.

Yes, Oasis is a brand name manufactured by Smithers-Oasis. The horticultural version is almost identical to the green floral foam, only it is brownish in color in the preformed Horticubes. The cubes hold up for a long time. If you're growing lettuce you're only talking about maybe 50-60 days total, or 21 if your Yoda will share his secrets. By that time the cube has become encased with roots which hold it together.

Here is a link that might be useful: Smithers-Oasis

I was able to get oasis floral foams. I initially bought 1 box. They don't have the horticubes but it won't be hard to cut them to the right pieces.

You are right about the 50 to 60 days. Because of the 21 days, I was starting to think that I was doing something wrong.

Thanks to you I don't have to drill the downspouts with 2.5 inches holes for the net pots. I've decided to make 1inch holes every 8 inches. If the oasis foams turn out to be expensive for commercial production. I will just use something else to hold them. It would probably look more professional if the nft holes were smaller.

I hope you don't get tired from my too many questions

What about rockwool for lettus...would that be an option?

What would be the difference between rockwool and the floral foam? What would be the better medium?

I have heard complaints about rockwool keeping seedlings too wet.

I was looking for articles about rockwool and one of them mentioned about not being able to drain enough water.

I think I'll use the foams. I will try to contact the supplier and find a way to get the horti cubes here.

The wire clips arrived already and we will be starting to install the covers for the greenhouse.

Adriana, I was looking thru other discussions and I saw the 5 days lettuce. Please let me know if you hear more about it

What about growing in pumice rocks only? It does not fall apart as easily as perlite, or does it?

Pumice rocks should work.

I'm presently using pumice rocks with my set up at home. But won't it be too much trouble to clean them every after harvest?

That is a good question. Pumice does stain after a while, so what is the best way to make the stain go away? What is the difference between perlite and pumice other than perlite floats more then pumice?

If I am remebering correctly, I read somewhere that you can clean them with a light bleach solution. You just have to make sure that the rocks are properly rinsed after cleaning.

Most washed rock will work just fine. Sillica stone or lava rock is really best though. Perlite is too messy and will float. Just look for a sterile medium that has a little weight and some surface area to it.

Yesterday I noticed teeny little rockwool cubes, meant to be used as the medium, not as the anchor. Oasis sponges are somethign different, aren't they? Has anyone used the rockwool cubes?

Yes they are something different. I am going with the floral foam that AdrianaG told me about. Its not very costly and might be more marketable if people see the roots attached.

I just came across your post and thought I would respond to it.I currently am employed by a small company called grow-tech inc. and we make an item we call a '276 mat'. It's like an oasis mat but its not made out of rock wool. It's composed of bark mulch,peat moss,polymere,minerals,and anti-bacterial agents.It feels,looks,and performs like a sponge.It's designed to promote rapid root growth,give the ideal water to air ratio,and it decomposes itself in 3 years I believe it is.We can make it into basically any shape,size,or design to meet almost anyones need.The '276 mats' we make are being produced for lettuce growers in the west to take the place of there rock wool they currently use.I've never tried to grow in the '276 mats' but do use there flexi-mix and other growing mediums in my home.I was amazed with the rapid root growth and success rate with these products. I can get a clipping to root in about 4 days and a seed will sprout to 3-4' high in about 3 days.I repotted a poinsetta in the flexi-mix about 7 months ago and its currently about 5 ft. tall now.I took a clipping from an ivy plant about 4-5 months ago and its currently about 12 ft. in length.Well I hope this helps you out..
www.grow-tech.com

Here is a link that might be useful: grow-tech

"It would probably look more professional if the nft holes were smaller." are you growing for yeild or for show? ~Ryan

mangojon,
Bataan, where you are from, is not too far from the lahar flows of Mt. Pinatubo. Lahar sand and gravel is in great abundance there. You are a lucky guy. You can get sacks and sacks for free. I have not used lahar or pumice, they are the same. But one thing sure, shortly after the eruption, vegetation in the lahar covered areas emerged in great abundance that means, the plants like lahar. Lahar is a blessing for farmers, especially mango farmers. Bataan mangoes are known for their sweetness. Can be attrbuted to the volcanic consistency of the soil in your area. Lucky guy.

mycarbumps,

Im trying to do both. I agree with you about the smaller holes, it would also mean less medium. I used perlite on my first batch, too messy.

cutter33_2000 - How does one purchase your products. I like the idea of a substitute for perilite and vermiculite

cutter,

Go to any hydroponics supplier and look for oasis grow cubes or rockwool grow cubes. That would be the closest to the one I am using. Here in the Philippines there are very few stores carrying hydroponics supplies and if they do, choice is very limited.

I still use perlite, but only for seed germination.

Hope that helped,

Jon

I will address your concern with power interuption if this is a concern then i would look into a solar array for your power needs. For about $1500 you could probably get what you need depending on your pumps power demand. if the interuptions are short then a UPS may work or you could buy some batteries a battery charger and a modified sine wave converter to cover your needs this last suggestion is probably your best option.

DBogey
just click on the link to grow tech and you can contact us.

could someone tell me the goods and bads of using 3/8" Pea Stone? Thanks

I guess no one likes the name gmac33?? I have posted 3 posts sine I signed on at Garden Web, and no one replies to my questions!!

Bye

I am using the raft system for lettuce. I have 1" holes in the styrofoam and I use the 1" oasis cubes that are like a wedge. I start the seeds in them and then put in the holes of the raft. Works great !!!

I am using the raft system for lettuce. I have 1" holes in the styrofoam and I use the 1" oasis cubes that are like a wedge. I start the seeds in them and then put in the holes of the raft. Works great !!!

Hi guys, do you know where we can buy rockwool cubes here in Manila?

Hi rouzen!
At the INTERNATIONAL- Hydroponic Forum we have at least two members from Philippines, and they might point you in the right direction or know about alternatives, near by resources, etc.

PS: non-commercial and public hydroponic forum - but needs registration to view content.

Here is a link that might be useful: INTER- Hydroponic Forum

Just for concerned people's information and a reminder for others: finding hydroponic supply of all kind in various countries around the world can indeed be a considerable problem. The idea of connecting such interest group for exchange of supply related- and other more common information is in fact one of the Inter-hydroponic forum's purposes.

I've certainly heard that hydro supplies are difficult to get your hands on in many countries. I've worked with a few people from the UAE and SE Asia that are interested in hydro (our work is not hydroponics-related, though) and say that it simply isn't practical due to lack of resources and high cost of shipping. I could definitely see the benefit of a network of interested people that might be able to at least split shipping costs, bank transfer costs, and buy in greater bulk for better discounts. Also, I'm sure that plenty of people in those countries have found alternative solutions to work around many issues. I can't say I see anything wrong with pointing someone in that position to a forum that might offer better solutions than this one. I would say that most people here are from the US and probably do very little international business. It's easy to say (as I have seen in other threads when someone asks such a question), "there are all kinds of companies that ship internationally". However, it is ignorant because it costs many times more than the product to ship it to SE Asia often times. It cost us $200 to ship a 2 lb sound level meter that cost $70 to the UAE last week through DHL. I know the UAE is not in SE Asia, but it is an example of the high cost of international shipping.