What kman said. XD got them from petsmart as well. =)

Yes, I know soil is dirt.

I'm referring to the substrate cap (the non-soil one that is theoretically in there now).

Unless we're crossing wires and I'm misunderstanding you, you're talking about a way to add dirt/soil to the bottom of an existing non-dirt/soil substrate (gravel, sand, etc), right?

Any substrate in an established tank is going to have all kinds of gunk trapped in it that you don't want to release without risk to the fish, even if you change the water, much will be newly-exposed and likely start producing ammonia and other junk in the water. So major disturbances to existing established substrate should be kept to a minimum. Even carefully "shimmying" in frozen blocks would be a pretty major distubance, if you're coating the whole tank bottom with them under the existing substrate (which would now be a cap for the dirt/soil).

Of course, if I'm misunderstanding what you're proposing, then perhaps this warning doesn't apply, and I'd love to hear more about this, because it does seem interesting.

(I mentioned the temperature issue because you said "Can also remove the fish if you want" but I don't see that as particularly optional for major work like this.)

Well, in my opinion, regardless of rinsing your substrate, you're probably going to have all kinds of gunk. That, and I also have a population of MTS in my sand, I'd rather not rinse the soil with them in it.

This thread has been super informative and I've got everything ready for my first NPT except plants and lights. Here's my question.
How many plants are the correct amount to safely plant and stock with critters on the same day? I have an 11 gallon tank with organic miracle gro substrate and sand cap. I want to make sure the tank is safe for my critters and need some help with how much to plant for the size of my tank. Thank you.
Puck

I wouldn't plan on setting up a brand new tank with capped soil, and put fish and such in it the same day. Plants, yes, but otherwise the tank needs time to cycle.

THanks for the reply and please forgive my questions but the OP Old Fish Lady's first post clearly says that you can plant and stock the same day if done correctly with enough plants. Is this no longer accurate info? I'm happy to plant, cycle then stock but from the OP it didn't seem necessary. My betta is perfectly happy in his smaller tank and I don't want to risk his health stocking the new tank early so thank you for the help.
Puck

I just started my first NPT using miracle gro organic potting mix with a sand cap. I was also under the impression that I could stock immediately too. However, apparently if you use the organic miracle gro it has an ammonia spike for the first couple weeks so it needs to cycle. It has been two weeks since I set my up and it just now lowered to .25ppm from 2ppm. I would be sure to test your tank before stocking. Hope my little bit of experience helps! :)

Thanks for the reply Summersea, your tank was one of the ones that really jumped out at me when browsing through this thread and your advice is appreciated since you used the materials in your tank I'm using. I will plant and cycle the tank before I add my betta. I'm going to take advantage of the Petco fish/plant sale on the 22nd and 23rd of this month.
Puck

Aww I appreciate te complement since I have never done this before :)

I definitely think you will love the results. I have been amazed by the growth in my tank! Make sure to get lots of stems! My wisteria absolutely loves this substrate and has grown amazingly fast! My hygrophila corymbosa and cryptocoryne wendtii have also done pretty well if you can find them at petco. I plan on taking advantage of that sale too - only I will be picking up a new betta for this tank! Good luck and be sure to post your results! I can't wait to see!

Thanks again for the tips, I'll be sure to post up some pictures of the tank when its put together. I collected a couple of nice rocks today to help add some interesting terrain for Eddie, my Betta. I am anxious to get started.
Puck