Although this is true, I wonder if the stems stay compact or continue to grow to the top of the water line. I'm not a huge fan of plants hitting the waters surface in small rectangular tanks (I have a fluval spec 5 I'm planting out). Its just not esthetically pleasing.
Yours look just about right. Does that red plant stay low or are trimmings necessary (and how frequent)?
All stem plants I have will reach the surface if you do not trim. That's just how they are. Nothing you can really do about it, except trim them.
I trim about once every 2 weeks in this tank. However, I don't trim that aggressively, meaning I don't cut a large amount off the top. I also don't wait until plants hit the top, except sometimes in back. I keep the low plants low, medium plants medium, high plants high, if that makes sense.
The only plants I have yet to trim are the two red plants in front of the wood. I have even trimmed the ground cover already, not since I started this journal.
Hope that helps, most plants, and basically all stem plants will need a proper trimming from time to time and the smaller the tank, the more often that usually is. CO2 or quick growth in general will lead to more frequent trimming. Trimming is what helps style a tank, which I hope will become evident as this evolves because I find it pretty ugly right now lol.