Hi Simon,
The substrate Capsules are good but you can easily replicate them by placing osmocote into an ice cube stray with a little bit of water, wait till it freezes and stick 'em into the substrate. This way you can save a lot of money as a bag of osmocote slow release fert will last ages.
In terms of liquid ferts I will suggest this
http://www.aquariumplantfood.co.uk/...tiliser/apfuk/apf-liquid-plant-nutrition.html
Dry salts are really not confusing, you can use them and mix it with water to make your own liquid fertilisers or just pinch some salt and sprinkle it in your aquarium. And in the long run dry salts are more cost effective than their liquid counter part because liquid versions come pre-mixed usually containing more water than the actual liquid.
Should you wish to go down the dry salt route, I highly recommend this :
http://www.aquariumplantfood.co.uk/bundles-starter-kits/bundles-2/starter-kits/ei-starter-kit.html
At the end of the page of the link I just provided shows a tutorial on how to use dry salts to make your own liquid fert.
Here is an article written by Clive which gives you a method called EI involving try salts, the method essentially involves placing more nutrients than needed in your aquarium to make sure there are no shortages. Here is the link:
http://www.ukaps.org/forum/threads/ei-dosing-using-dry-salts.1211/\
You have not mentioned this but I believe you don't use CO2, in which case it is unlikely that you will need as much nutrients as proposed by the EI method, but it is not harmful to add more than need.
If you do not like to waste a lot of money by giving extra nutrients you can try a method proposed by Darrel. It is called the Duckweed Index, it involves using floating plants as indicators to show if you need to add nutrients or not. This is helpful because floating plants have unlimited access to CO2 and light therefore, these two factors can be disregarded if the plant is not doing good leaving nutrients as the limiting factor to growth. In this thread Darrel outlines different methods of dosing including the duckweed index
http://www.ukaps.org/forum/threads/water-column-dosing-and-substrate-questions.1669/#post-359607
In this thread Tom Barr outlines his take on the low tech method to growing plants, he also gives his recommendation on dosing a low tech aquarium using dry salts.
http://www.barrreport.com/showthread.php/2817-Non-CO2-methods
Here is also a very useful thread by Troi which explains how he would use soil in a planted tank. While you have already setup the substrate, this thread gives a lot of good fundamental information regarding the planted aquarium which is very very useful in my opinion.
http://www.ukaps.org/forum/threads/the-soil-substrate-planted-tank-a-how-to-guide.18943/
Regarding the plants being placed next to the output of a filter, you should not need to worry about this. As far as I can tell you are keeping Vallis at that spot and they to high flow quite well so no need to worry.
Michael.
.
