I have a bucket of seaweed I scored from work. I was going to dry it and make kelp meal with it, but then we got a boatload of rain. Fast forward two weeks and the bucket is still there, seaweed, water and all. I stir it almost daily(at the expense of my wires sense of smell), but don't aerate it any more than that How safe is this concoction?
I make something very similar with my own native seaweeds. The only thing is im not as fortunate to have my bucket filled with rain water. If you really want to be cautious. Take about a cup of the solution and dilute to a gallon of water. I always make a "test run" also. I basically spray it on one plant and watch it for an hour or two. If it looks ok you're good to go. Im more than confident that you dont have to dilute. But thats just the cautious side. You can also take the strained seaweed material and feed it to your worms or compost it. Good luck, but im more than confident that you should be fine...
Sean gave you good advice. Do a test run on one plant. Do you know what variety of seaweed you have? There are major differences between different varieties of seaweed and the nutrient profile each variety provides. The best major strain that most kelp meal is derived from is brown Norwegian kelp - Ascophylum Nodosum. I'm sure that other varieties are good; Ascophylum just has the best variety of elements and compounds/growth regulators. If you find your tea isn't what you hoped for there's always the compost heap.