oh man, where to start.....

first, I would DEFINATELY recommend NOT using miracle gro.

Miracle Gro receives ALL of it's nitrogen from ammonia and urea. Both forms of nitrogen require bacteria in the soil to break it down into a form that is usable for plants. There is no soil in hydroponics and therefor all the nitrogen in Miracle Gro is wasted.

The addition of calcium nitrate in that formula is required for usable nitrogen.

Furthermore, ammonia and urea (nitrogen in Miracle Gro) will lower you ph. If you use enough Miracel Gro for your plants to get enough Phosphorous and Potassium, the amount of ammonia and urea that you will be adding to your solution will throw your ph ALL out of whack.

I understand where you are coming from (I was there once myself). You want to use inexpensive fertilizers that are readily available to you.

I'm going to share with you the "golden-egg" that someone on this forum once shared with me.

Find a golf course/nursery/landscape supplier in your area (probably the cheapest place to get calcium nitrate anyway). Choose a fertilizer that gets all (or very nearly all) of it's nitrogen from nitrates. The formula I buy get 85% of it's nitrogen from nitrates. Remember that ammonia brings ph down....well, the 15% ammonia in my fert keeps the ph in check. (ph would normally rise slowly as the plants used the nitrogen if it was all from nitrates) You should be able to get a 25 lb. bag of a good fert for somewhere around the same price as Miracle Gro or maybe even cheaper. I pay about $25 for a 25 lb. bag. $1 a pound is very very reasonable. I have a couple 25 lb bags of 10-20-30 and that will be enough to last me for years.

Once you've chosen a good fertilizer, do a google search for "N-P-K calculator" or "ppm calculator". You can calculate how much of your chosen fert to use per gallen of water, in order to put nitrogen at 200 - 250 ppm. As long as Nitrogen is somewhere between 200 - 250 ppm, everything else should work out fine for a hobby gardner. I also add calcium nitrate, but I figured that into my calculation to get nitrogen between 200 - 250 ppm. Chances are that you will be very pleased with the results.

Now for your questions:

"How much water do you use with your nutrient solution?"

That depends on the size of your reservoir, type of system, amount of evaporation loss, number of plants, etc. I use 15 gallens of nutrient for my system.

"When it gets weak (how do u tell?) how much solution do u add to make it stronger?"

You can purchase a ppm meter to tell when the plants are using up all the nutrients. I don't use one. I just change my solution regularly.

"How often do u HAVE to change the solution?"

Every week or two. Sometimes I change it every week. Definately every two weeks, if not sooner.

"Is this solution good for anything (i.e. does your lawn like it?)"

soil based plants will love the left over solution (including your lawn).

Hi Thebonepile,

I invite you to look at my Australian web site. It explains everything you need to know about hydroponics.
It shows how to make a sand system, how to make your own nutrients and adjust them, hints for success and an FAQ section. The web site is shown below.

Now for Urea and Sulphate of Ammonia. Both are NOT suitable for hydroponics as explained by Jdog006 above.
Both have ammonia nitrogen which needs soil bacteria to convert them to Nitrate nitrogen. Most plants like their nitrogen in the Nitrate form.

Urea does not affect pH, however when it is heated, dry, it gives off Ammonia and Biuret. Biuret is not soluble in water, but Ammonia is freely soluble in water to give Ammonium Hydroxide which is alkaline and raises pH.
My site shows how to make your own nutrients from scratch, although, unless you are really dedicated to the task, most people go for prepared mixtures, which is the easiest way if you are starting out or just growing a few plants. As you gain more experience, you will want to make your own.

If you save each page of my web site to your computer, all in the one directory, then you will be able to navigate from page to page in a flash, when you are off-line.

Jimr007
Australia.

Here is a link that might be useful: Simple Sand Hydroponics

What are you growing & what is your system? Some growers do use Miracle Grow, & it can be used to experiment. Some short term crops will grow with it, but will develop deficiencies with it. As growers grow more in hydro, they often go on to hydro nutrients.
You can go to your local hydro store & ask for their cheapest solution. There are some all purpose grow solutions for about 15.00. It is better to buy locally than online to pay for shipping. If you are using a pot or run to waste system, you mix it according to directions, add to your plants & flush routinely. If you are using a recirculating system, than you need to get an EC or ppm meter.