I have previously talked about my techniques for germination and early stage growth of pepper plants. Once the plants get some size to them it is time to plant them into some better soil and bigger containers. In this tray below is what is left for me in the 2018 season. I have went through 2 plug trays twice and now refilled half of one. Some of these are now big enough to plant up. I will dig them out of the cells with the craft sticks shown on the left. It is easy and safe to separate the multiple plants growing in the cells. They are pretty tough and can be safely separated.
There is almost limitless choices of potting mix to use available in the US. I have settled on Fox Farms soils. I like to mix the Ocean Forest and Happy Frog. They have done well for me that last few seasons and I see no reason to change. I have not had any problems with fungus gnats or other pests with this soil. I have had other soils that seemed to harbor pest eggs and/or even some disease. This soil has enough nutrients in it where I typically don't add anything else for a month or two. You can use any soil you want, I just recommend something light that will drain well. If its too heavy added perlite may help If you use something that is fertilized and advertised to feed for 6 to 9 months, you may not want to add any nutrients for quite some time, if at all, as it may have enough already. Sometimes excess nutrients can be worse than too little.
The container size you choose to plant into in this stage is completely up to you and your needs and goals. I normally get most of my plants started early. Most of my chinense strains that I focus on mostly are typically potted up by the end of February with a handful often not until early March. My plant out time is typically mid May but can vary to early or late may depending on the weather. Due to limited space I don't use particularly large containers. Most of my plants will be planted into 3.5" square pots. I like these as they typically are big enough to get a good sized plant and 18 of them will fit nicely into a 1020 flat. The other container's I use a lot are 606 deep cells sheets. These fit 36 plants to a 1020 flat. This is pretty tight and not ideal. I do this for later starts and secondary or less important plants. It saves space and most of the time the plants do fine but will be quite root bound. I will have to trim and strip some of them to help with air flow and spacing, etc. I try to keep my flats to a minimum also as during hardening off it can be a pain to move the flats outside and back in for a few weeks. A greenhouse would help with this but it is something I don't have. My recommendation would be to use at least 3.5 inch containers. Some people use a gallon or more. It all depends on how much space you have, how much capacity for moving, funds for soils etc. A lot of people use solo cups with holes poked in the bottoms for drainage. Another option I see a lot of people doing is double cups. I have not done this and would have to refer you to google or youtube for your own research on this method.
Now that I have my containers ready I mix the Happy Frog and Ocean Forest in a bucket. Usually I use about 60 to 70% Ocean Forest but don't measure. I wet it and mix it up in the bucket as it seems to not absorb water readily sometimes. I then fill my containers or cells and make a small hole in the middle with the craft stick where I will place the seedling. Now I will remove the seedlings from the plug tray and separate them if there is more than one in the cell. Either way I discard most of the seed starting mix before planting into the new home. See the pictures below to get an idea of what I am doing here.
Now I will put the trays under lights. I run the lights about 16 to 18 hours a day. Basically the peppers sleep when I sleep. When I get up in the morning I turn the lights on, and then turn them off before I go to bed. You can use a timer for this which I do sometimes if not going to be home to follow my routine.
As you can see I am still low tech with all of this. I am mostly still using tube lights. I do have some led 4 foot tubes now but also still use some t8 fluorescent lights. Someday I plan to start experimenting more with the newer LED grow lights, but for now this is what I use. I do have a small 2 foot red/blue led grow strip on the ends of a few of the shelves above so I can get good coverage on 5 flats. I don't use a grow tent or any reflective sheeting. While these might be great they just aren't something I need. Like I have previously mentioned, I don't want my plants growing too big too fast. Any better lights or tents or heat etc would fine, but if you don't want to spend the extra money its not required. Depending on your conditions a fan to circulate the air might be a good idea. I don't normally use one because my basement is relatively low humidity and I don't need one. If you have higher humidity it might be a good ideal. A fan can also help produce a stronger seedling as they will be reacting to the wind and can grow stronger. I am looking to get a fan possibly for that reason.
After they have been potted up for a month or two I will start to fertilize. I may start sooner if it looks like they need it but rarely do. You could research fertilizers until your head explodes. I know I have. I try to keep this as simple as possible. The past few years I have used the Fox Farms fertilizers Big Bloom and Grow Big in the early stages. Some friends and other people use complex high end nutrients that come in different parts, all sorts of additives etc. Its just all too much to think about for me. I found a fertilizer that worked great in my container grows last year. It was so impressed I decided to try and use it exclusively for everything this year. I contacted the company and I believe was emailing with the owner. This fertilizer was Urban Farms Vegetable Fertilizer. It was so simple to use and the plants loved it. After communicating with the owner he recommended for early grow to use his Flowers and Blooms formula and for the first month or so then switch to the Vegetable Fertilizer and ride it out. That is what I am planning to do and have no reason to believe it won't work. All you have to do is mix with water and adjust PH if needed to get it in the 5.5 to 7 range. With my high PH water this fertilizer doesn't need any PH down as it seems to be a bit acidic and after mixing is just right. I'll start off probably at half strength and work it up to full strength over time.
You can probably use any fertilizer you want or is readily available. Some people make their own compost teas. I just don't have time for all that and this worked well. Whatever you choose, don't over do it. Less can be better than more so best to ease into it. Probably the most important thing is to be sure your PH isn't too high or low. I normally shoot for 6 to 6.5. I battle high PH with my water here so my main focus is to be sure that every time I water and feed the PH is 7 or less.
Once the plants start to get too big and crowded I will have to do some pruning. This subject is discussed in great detail in pepper forums. Some people start topping plants as soon as they think its safe. Others never do it. I have a mixed opinion on it myself. I have topped a lot in the past mainly because my plants are just getting too tall too soon before planting out. I have personally not seen a great difference in production by doing this. Some people swear by it saying they get twice the production as it can help create a bushier plant with more nodes. I think with certain varieties this is true but with others it just doesn't matter. I would say do you own research and make your own decision on this. I will prune and top as needed mainly due to space constraints. If they are getting too tall I will be topping them. In the trays where I have 36 plants I will be doing a lot of lower leaf removal to provide breathing room.
One of the last and maybe most critical steps is hardening off. This is critical if you haven't been growing them outside or in a greenhouse. If plants are not hardened off adequately or at all they might not survive planting outside. This will be particularly bad if you are in a hot environment with a lot of direct sunshine. If the plants have lived their entire lives without seeing the sun it is a great shock to them to be suddenly exposed to it full time. I normally stat trying to harden off my plants as soon as the weather permits. Sometimes this is in mid or even early April. I usually start by bringing them out later in the day into shade or indirect sunlight.
This basically sums up how I do this. Low tech, no hydro, no tents etc. All that would be great but just something I don't do. This basic setup has worked for me for nearly 20 years and I am slow to change. If you want to invest in some of the other equipment I have mentioned then that is great. You may be able to get quicker growth and better plants than I do at a younger age. It is just something at this point I don't need. Once I put my plants outside they usually take off in the warm sunshine. Often by years end it is difficult to know which plants were smaller at planting, which ones were in the 36 cells per flat and root bound. They all seem to even out. Sometimes though if you have the space, lighting and time to get plants up to 1 gallon or more containers early on you can get pods much earlier in the season than I will.