Hey Caliban, I don't have experience with either of those two specific plants, but will advise on similar plants I keep in my tank. The Bacopa grows like Rotala, so just snip it above the leaf at the desired height. You can replant the top by pulling the leaves above the cut off for an inch or so, and place into the substrate.
For the wisteria, I would guess its closer to the Water Sprite that I keep, and I usually trim it near a place where the stems branch out or look like a Y. I will snip it off just below the Y and then replant the trimming just like I trimmed it, leaving a nice looking new plant!
I have found that when plants are healthy you can really do no wrong when trimming(within reason!) it usually stimulates growth near where you trim. I would just say to be conservative at first, get some trimmings growing as new plants, then you can get more aggressive and scape or cut them to your liking!
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Never kept it my self but here is its profile from LiveAquaria.com:
QUICK STATS
Care Level: Moderate
Lighting: Moderate
Placement: Background
Water Conditions: 72-82° F, KH 3-8, pH 6.5-7.5
Propagation: Cuttings
Max. Size: 1' 8"
Color Form: Green
Supplements: CO2 Fertilization
Origin: Farm Raised, USA
Family: Cabombaceae
overview
The Cabomba, also known as the Carolina Fanwort, has feathery green leaves, which are divided into narrow segments. It is a densely growing plant that makes for a wonderfull, natural looking background in a planted aquarium.
Cabomba does best when grown in nuetral water under moderate lighting. Provide at least 2 watts per gallon of full spectrum (5000-7000K) lighting. Water temperature between 72°-82°F, an alkalinity of 3-8 dKH and a pH of 6.5-7.5 is ideal for proper growth. These plants do not tolerate frequent trimming and transplanting. Leaves dropping from the plant are usually a sign of poor water conditions or CO2 deficiency.
Propagate the Cabomba by trimming branches from the main plant, and relocating them in another part of the aquarium. It should be placed in the back or sides of your aquarium in groups for the best appearance.
I want some of this plant now!!! Love it's look, now what plants to take out....
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Haha thanks. It grows real quick and was doing fine before I cut it. How do you tackle the height issue if you can only trim off branches? Hmmm
Hmmm indeed! I got nothing.... Will have to think of something though cause I placed an order for some last night! Maybe tie it back down over itself? Or plant it sideways? Lol!
As to the wisteria, yep if anything like Water Sprite it will grow from the cut off point and fork out and grow in thicker.
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