10.00 question
 

Is there a chart or rule of thumb for plant placement[distance between plants] for hydroponics

in the dirt world their is recommended spacing if plants in rows [and distance between rows]

specifically tomato and bell pepper plants

I am really getting into the hydroponic farming due to lack of soil here in the U P of Michigan

got the sauna house redesigned with glass on the south side and loaded with plants

Doc.

General rule of thumb for plant spacing is to take into consideration the full size of the plant being grown. That is how big it gets when it's full grown, then space that distance apart. Closer spacing could require excessive pruning to compensate for crowding, and/or lead to inadequate air movement between plants and foliage. Inadequate air movement can also lead to fungal diseased, as well as pest infestations.

Another problem with crowding inside a greenhouse with inadequate air movement is rapid c02 depletion. The plants will still use the same amount of c02 weather they are crowded or not, but if there is inadequate air movement between the plants and foliage, the c02 the plants use cant be replenished fast enough through air circulation. Then the plants growth will slow or even stop, they simply cant grow without c02. Plants get all their carbon (c02) from the atmosphere, and carbon is the basic building block for all plant and animal life.

P.S.
You can help air circulation by using fans, especially oscillating fans that move back and forth.

Article on Density Effect
 

A few months ago I read an article entitled:

“Spanish” Pepper Trellis System and High Plant Density can Increase Fruit Yield, Fruit Quality, and Reduce Labor in a Hydroponic, Passive-
Ventilated Greenhouse

The paper described a research trial conducted by scholars at the University of Florida in which they varied the plant density and pruning method of red bell peppers grown in perlite. In general, they found a linear increase in yield and quality (defined as "marketable peppers" and incidence of blossom end rot) for non-pruned peppers at high density (defined as 3.8 plants/square meter, which is approximately 2.75 square feet/plant).

In other words, you can save yourself a lot of time and energy if you don't prune your plants; in addition, you can save space by spacing your plants relatively close to one another - as they occur in nature.

Naturally, there are limits to how close you want to put your plants. As GpsFrontier stated, crowding can cause poor air circulation and fungal development. In terms of pruning, I don't manipulate the development of pepper plants too much; indeterminate tomatoes, however, can become unwieldy quickly and deserve a few bouts with the clippers in my humble opinion.