I grow Ghost in pots, the get about 3-4 ft tall and wide for me, not sure how they will do in a greenhouse in a hydro setup, I would estimate around that size their first season. As for the temp 80-90 degrees at the most. They can handle higher temps but if they are flowering they will likely drop the blooms just as they do in outdoor environments.

Can't comment on the hydro portion will have to leave that question to someone experienced in that aspect

Yea how tall they get isnt really an issue. its more of how wide they should be spaced apart from each other.

Seems to me that the principle consideration is light. You space them at least as wide as they get so that the leaves get maximum light. Otherwise there's really no detriment to letting the leaves overlap.

In a relatively high-light environment, I would say spacing is not critical. Are you using natural light? Glass roof? How many hours?

Im using 4mil polycarbonate panels & roof. Im in Northwest Washington zone 7B. Im thinking like 1.5 or 2 feet apart?

They get 3-4 feet wide as they mature, in one season or at least for me they have. While young seedling the 1-2 ft will be fine. But the conditions for me are outdoor in pots.

Here are some visual's

Young plants Ghost Chili

Older but not bearing fruits yet

At the point to where its flowing and bearing fruit

Top shot of the same plant

The Bhut Jolokia

are those over wintered. reason i ask is i noticed the size of your pot and the ripe bhuts. i am wanting to over winter. will be my first year.

Those are one season plants from last year. Pic was taken end of June or early July. I posted the pics to give a visual for spacing. This year my Ghost is still young, though my Red Hab is just about the size of the above ghost because I started some seeds back in December.

I will post a few pics of my dwc spacing when i get home.
but my super hots they are within a foot of each other...
i dont mind the clutter mainly because if grown correctly they will get HUGE - most of mine are 5ft or taller it is kinda of a pain to keep staked so i let them lean on each other. plus helps provide a little shade in this brutal florida heat/sun.
as far as nutes goes. GH Flora Series all the way. and get a bottle of the GH rapid rooter as well... it is like steroids for seedlings.
Temps dont seem to matter to much with my plants... it is 97 out today and they dont show even the slightest sign of stress or fatigue. i would recommend keeping the nute solutions cooler if possible but it isnt a really game changer.

Hab, I noticed how large your leaves are and dark green. On my 2 Bhuts; they are in the ground, clay soil in Texas. I have only fertilized these once, when they were first put in and about a foot tall. Now they are 2 feet tall, but the leaves are small and kind of regular green, not pale or in anyway yellow, but certainly no where near as dark green as yours. My questions: do pepper plants need fertilizing in the ground? I was told they dont need fertilizer but epsom salt and only when leaves were yellow. Because of the 100+ temperatures her, the plants only have one fruit on them and are dropping flowers. In this perid of no fruit, should I give these plants a boost of a balanced fertilizer like maybe just plain miracle grow 10 6 8?

Hi Darylltx, I tend to grow in pots and fertlize. This season I do have 4 pepper plants in the ground. I don't fertlize them as often maybe once every 2-3 weeks and when I do I use Alaska Fish fertlizer 5-1-1. Most of July last year was flower drop then pods set and was able to harvest until the end of my season October.

In pots I use the same fert as above and Epsom salt, don't think the in ground really need it and often the Nitrogen in the fish fert resolves any uptake of mag in ground to fix the yellowing leaves.

daryltx. i used a 11-15-11 granular fert with some bone meal in the ground and a fish fert as a starter solution. after they got established i did what habjolokia did. used fish fert, seaweed and a liquid calcuim as a foliar spray every three weeks. put a shade cloth over my peppers first time in years and now i am reaping the headaches, but it has helped increase yeilds and i also plant my peppers foot apart.
this is my first year growing bhuts found it is not to hard as long as you keep them close. hope this helped from my limited experience with bhuts.