Aggressive Gouramis

I've had a 55 gallon tank running for a while now, and its nicely stabilized and looks great. I'm running a Rena XP3 and an Emperor 400 for filtration. I've got plenty of biological media, and everything seems to be running smooth. My tank parameters are as follows: 81 degrees F, ammonia - 0ppm, nitrate - 20ppm, nitrite - 0ppm, GH - 25, KH - 120, pH - 7.8. I change out approx. 3 gallons of water every other day (giving me about 20-25% weekly change), and siphon the gravel once a week. My current residents are 2 opaline gouramis, 3 clown loaches, a chinese algae eater, a pictus catfish, and an eclipse catfish. The opaline gouramis are approx. 3" each, clown loaches 2.5" each, chinese algae eater 4.5", pictus catfish 5", and eclipse catfish 6". I have also recently adopted a 6" common pleco, which is currently in my 10g isolation tank by itself making sure that there is nothing wrong with him... though I am not sure if adding him to my community would be too much. (and yes, I realize that most of these fish are going to get 6-8" each, and that the pleco will get much larger than that) I intentionally have excessive filtration on my tank and perform very regular and frequent maintenance with the hopes of keeping this tank healthy and happy, even though it is a bit overstocked. My question for all of you (and my apologies for taking so long to get to the point, but I wanted to give as much background info on my tank as I could to facilitate diagnosis) involves my gouramis. I've never kept gouramis before, and they are the newest residents of my tank. I got them 5 days ago. I have one male and one female, and I have noticed that as time has progressed, the male has become increasingly aggressive towards the female, but leaves everyone else alone. He frequently chases her along the entire length of the tank and even through some of the plants. (fake plants) Is it common for male opaline gouramis to be so aggressive towards females? Would adding one or possibly two more females alleviate some of this excess tension? I'd like to keep the gouramis, as they are very pretty and fun to watch, but I am slightly concerned about the male chasing the female so much. Thank you for taking the time to read my post.

Is it wise to consider introducing the pleco? Or would it be best suited if I found him a better home? I personally don't mind doing a lot of regular maintenance, but I'd like for my fish to be healthy and have the freedom to move around. I am considering upgrading, but that won't be able to take place for at least a full year, possibly a bit longer.

I fully understand that they get very large, even in captivity, but I am unsure as to how quickly they grow. I've had customers tell me that it took their pleco well over 4-5 years to hit over a foot long, but I'm willing to bet that this is at least partially attributed to a poor diet and less-than-adequate swim room. Being that he's already approx. 6" long and about 3-4 years old, do you feel that his growth has already been stunted by quite a bit? I'd love to see 'em in my tank, but at the same time, I know I have nowhere to put a 200+ gallon tank until I move out next summer.

Well, if it is helpful at all, his color patterns are slightly different than a "typical" pleco which you'd see for sale in a petsmart, petco, etc. He's got a lot of reddish-browns to him, and some small bits that I'd even say are red, unlike the "typical" brown/black you'd find on most of the ones for sale. Unfortunately, I have no way to post a picture of him, primarily because I haven't got a digital camera. (my scanner's busted too, otherwise I'd take a regular picture and have it up in about 2 days) I realize that this probably has little relevance to determining what species it is, but at least it contributes to my reason for wanting to keep him. (beyond which, I know his previous owner, and I told her I'd take good care of him)