Besides from the usual NPK nutrients, what's something I can add to a potting soil mix that provides the majority of trace nutrients through slow release? Will granite powder do most of the work?

Eventually Slow Release will run out of steam. Then you can only top dress. So then that will act like liquid fertilized anyway. This is my first year doing container planting, mostly peppers and a couple of tomatoes. So based on the recommended practice in this forum, I mixed some SRF to potting mix. Then I will have to read my plants and may fertilized with reduced strength liquid fertilizer later on. Both SRF and liquid fertilizer that I am using have 3N-1P-2K ratio.

Peat starts out at a very low pH and is adjusted upward by adding lime, which also supplies Ca and Mg. Coir starts at a pH that is already too high (around 7.0) for container media, leaving no chance for using lime as a Ca/Mg source. So what are you using that ensures your plants are getting the Ca and Mg they need, and how do you address the high pH issue that needs no attention with bark/peat-based soils? How do you know you're getting your coir/CHCs from a reputable packager? and that the solubles level isn't excessively high ..... until your plants are surviving or failing? Seems like an unnecessary risk to me. Lots of things become the rage when people don't understand the product well. It's only after they've been brought into the light that people start to say, "Hey wait a minute". Lots of people simply decided that coir (or CHC's) are a great idea based on the fact that THEY bought into the idea that peat is not renewable and they wanted to feel they made a wise choice in switching. Look at the impossible claims you hear about products like Superthrive, Eleanor's VF-11, Bloom-booster fertilizers ...... A few people repeat something they heard someone else say, and pretty soon it's an urban legend and touted as the best thing since sliced bagels. There are reasons commercial ops don't use significant amounts of coir and CHCs in media - cost, high levels of soluble salts (are common) and a pH too high to deal with w/o acidification of the irrigation water. "Isnt the point of drainage layer so there isnt a saturated layer at the bottom of the pot?" It may be your intent, but wishing it would work that way doesn't change physics - no matter how hard you wish. 'Drainage layers' do not promote drainage unless the particles in the drainage layer are no larger than 2.1x the size of the particles in the soil. If they are larger than that, water 'perches' in the soil above the 'drainage layer'. "If the styrofoam was rock I could understand the water perch idea." Rock or big chunks of foam make no difference. The water reacts the same way. "The op was asking about making containers lighter. Annuals and alot of plants dont need the 20+ gallon size of large containers for root colonizing. Why have a 100 pound pot if you dont have to. What would you suggest?" One of the best ways, from a scientific perspective, would be to upturn another (plastic) container inside of the one you're planting in and put a screen over the drain hole. Second best would be to insert a false bottom with a wick through it. You could also partially fill the container with soda bottles or milk jugs with screw-on caps. You CAN use chunks of foam or peanuts to reduce the amount of soil needed to fill a container, but these layers of material in the bottom of containers do nothing for drainage. Al

How exactly do you figure seaweed or fish emulsion isn't organic? ;) And no, I wouldn't cut up your old sushi seaweed sheets (really biting my tongue on that one because it's seriously cracking me up, I find it pretty adorable). Whether or not your seedlings need more fertilizer than provided by the worm castings is really a pretty complex question, depending on what else is in the soil, what type of plants they are, how old they are, and how fast you want them to grow before you can plant out in your zone. Myself, I don't bother too much with extra ferts unless I need to stimulate growth or the plant is a heavy feeding variety, but when I do, I use a very diluted fish emulsion and only on mature seedlings (several sets of true leaves). It sounds to me like you've got the seedlings in some type of soil, ie not sterile seed starting mix that has no nutrients at all, so they're probably fine as is unless you have a reason to think they need more ferts.