Some people may disagree with me here.. but a lot of the bio-load depends on how much you feed. Extra food that ends up at the bottom add a lot of extra bio load to get rid of the rotting waste. Your Fish will always act like they want more although they dont need it. The 1" to 1 gal rule is always a good rule to follow, but can be bypassed. I agree that the pleco is a high bio load fish, but any algae eating fish will be more than others, they are always finding something to eat. Fish such as a neon or zebra that only really eat what you put in depend on what you feed.
Where i have been able to get away with more than the rule is fish such as the neon or zebra. If you do it slowly you can introduce more to your tank , but should something go wrong with your tank, its going to wipe the whole thing out. nitrogen cycle with an overload depends on stability constantly.
Most will agree with this here. 80% stock is a great number to follow by to give yourself leeway if something happens.
Also do not forget. Watching what your fish do is the most important. The gills should be a bright pink. If they turn a blood color , the ammonia is too high and showing signs on ammonia poisoning. If your fish are tending to stay at the top , they are looking for oxygen. This is a tell tell sign of a PWC (partial water change).
Now if only one of your fish are hanging around the top , then there is something wrong with it. The fish can not process the oxygen through the gills. This could be a sign of many things. But if it is solitaire, and all the other fish are fine , its something that can be starting. It could effect everyone, or it could be that it got into a fight and is hurt.
Another thing to keep in mind. The higher the temp is in your tank , the less the oxygen saturation is going to be in your tank. Lowering your temp about 2 degrees over a day and adding an air stone can help. But do not let the temp drop anything more than 2 degrees over a day , it can shock the fish.
Fish can be easy , but they can be hard. Taking time to see what your fish do on a regular basis and knowing that they are not normal is the key.. Also google is the other key. You can find anything on google, and as i found out , there are so many people on here that can pinpoint something fast. Dont be shy, ask.