| | Re: New with some questions
Hi Shane, and welcome to APC!
1) Yes, the aquarium gravel will work fine as a cap for your soil. Don't put in too much soil--a 1" layer is plenty.
2) It depends on your soil and how much preparation you have done to it. Rich soils that have not been mineralized can release enough ammonia for a month after being submerged to be unsafe for fish. Soaking and airing the soil as you have done helps. I suggest that you at least soak and drain it several more times before you use it.
3) I am not a fan of Coralife products, but opinions will differ. In any case, two T5 HO tubes over a 26 gallon will probably give you high light. This may cause problems with algae, especially at first. I suggest that you aim for medium light, which would be one T5 HO or 2 T5 NO. If you buy a 2-tube HO fixture, try to get one that will run with just one tube installed. Or get one that has two switches, one for each tube.
El Natural (a.k.a. the Walstad method) is a great way to start the planted aquarium hobby. After 3 to 6 months, these tanks become very stable and easy to take care of. I think the most common beginner mistakes are soil that is too deep and too rich, and having more light than you need.