I added clay (from the creek) to my 75 gallon as a plant substrate. The water is still cloudy and I think I added it five days ago. I turned off the filter when I added the clay and haven't turned it back on yet.

Can I turn the filter on now or will the clay break it? If I shouldn't turn on the filter, should I just wait or do a large water change?

I plan on adding a little sand on top to keep the water from getting cloudy again.

Unless you plan to run without a filter I would never turn the filter off. It will get cloudy from the sand also. If it doesn't settle in a time you like, do a water change.

So it shouldn't be a problem for my filter then?

Does pool filter sand cloud water after it's washed? I need something on top of the clay. If this clay gets disturbed at all it clouds the water and I might get corys or some other fish that prefer something smoother than gravel.

No matter what you use it should all settle eventually.

You could get small polished gravel it works very well with cory's..

Anytime you plant, you will stir up some of the clay causing minor clouding. Shouldn't be much to worry about after it settles. Sand will as well cloud after you first put it in. Just be sure to rinse, rinse, rinse and rinse again first. Pack you filter with extra poly-fil and that will help the cloudiness.

Carl has good advice for setting up the substrate in a planted aquarium here :Freshwater Aquarium Plant Care; Substrate, Ferts, CO2, and Lighting.

Basically, you want ot mix the fert (or clay, if you like) with a portion of rock or gravel. Cover it with a layer of sand about 1/2" thick or better (you want to wash the sand, first.) It's not strictly necessary, but I like to add a layer of river pebbles on the sand layer.

You'll always stir up some sediment when you plant. If you do it this way, though, the pebbles will help keep the sand down, which will help keep the clay down.

I use a secondary sand filter when my water gets really cloudy. it's a 2L soda bottle packed with pool sand about 1/2 full with a layer of filter cloth on the bottom (under the sand) and holes poked in the bottom. I siliconed a length of tubing into the cap and made a plywood stand that suspends it over the tank (works like a toilet seat for the bottle). The tubing hooks up to a submersible pump. I cycle the tank through this for 4 hours or so whenever I plant and it leaves the water crystal.

My water is still cloudy after having the filter on for a few days. I haven't bought the pool filter sand yet but I think when I do I'm going to make something similar to your sand filter because it's really cloudy.

Would 4-5 inches be to deep of a substrate even with plants? The clay alone is 2-3in and after I add the sand it will be 3-4in if I add 1in of sand. After that if I add gravel just around the bases of the plants it could be up to 5 inches. Should I take out a little clay and/or just add a 1/2 inch of sand?

I read more about swords and crypts and they should have deep enough roots to keep my substrate aerated so I figured that out.

It was slowly getting clearer but for some reason it's super cloudy again today. I haven't done anything but feed the guppies flake food. Why would it get cloudier?