having played with temps and outdoor hydro (more than played, actually), task #1 would probably have to be shielding your black tray from direct sunlight (without shielding your plants). Would it be possible to wrap the outside of your black tray with a white painters ground cloth? Held to trays with clips at the top and trimmed for a good (but breathing) fit? Will defer to others for your other good questions.

p.s. If this applies, your first task should actually be lifting your entire system off any outdoor concrete slab that that sits in sun (again, if this applies). A container's direct contact with concrete can be a massive temp influence, either hot or cold. Someone in the citrus forum last Winter alleviated bad concrete influence with 2x4 lumber, but I applied it to Summertime hydro. Such insulating lumber can help solve unlevel concrete issues with larger systems as well (as in my patio).

alright i think ill try that. But what about the inside of the tank? That still gets direct sunlight, and i think thats the main problem. Any more suggestions?

Oh ya sry i forgot to mention, this is inside not out. It is on a wooden table, next to a large(3' by 5') foot window that is facing west. So if anyone has suggestions for that...

will watch for further suggestions, but just wanted to confirm that I was referring to myself (not you) when talking about having "played" with hydro. I would think any regular member here has more experience than I do. :-)

Good suggestions, onewebfoot. The heat from the asphalt/concrete is already frying some of my plants in pots. Fortunately I grow a lot of cacti.

I donÂt know if this would work, but have you tried an upward draft fan or camping air conditioner under your table?

By camping air conditioner, I mean the low tech devices in which something like a laptop fan is placed on top of a cooler of ice or frozen soda bottles. The coolers cost about $40.00, but I have seen cheap do it yourself plans on e-Bay. You could probably get a cooler at a thrift store, buy a 12 volt fan & make one yourself.

Here is an example, although I have no idea how well it works.

http://www.kooleraire.com/images/KoolerAire%20Unit.gif

HereÂs another link for using an ice chest as a nutrient reservoir:

http://forums.gardenweb.com/forums/load/hydro/msg041115104587.html?8

I am adding soda bottles to my tanks, although I am seriously considering making ice cubes of some nutrient to see how it works. The soda bottles work, but melt very quickly with the heat. And the intense heat is yet to come.

alright the table that it is on has slats, about every 6 inches, but they are loose, and i can move them. What if I take frozen soda bottles, use bungee cords to hold them up against the bottom of the tray, and have that cool it down? would that work?

You might line the inside of the tray with a white line (plastic shower curtain) to prevent the absorption of heat into the black plastic.

Another possibility is to build a simple cover for the tray using styrofoam insulation (Dow Blue Board or Corning Pink) with holes cut out for the individual plants.