great tank there, the problems i see (and im no expert) but :
1: you have asked several times about keeping the bristlenoses , and have been told about how messy they are and how inefficient they are at cleaning algae compared to other species of fish ARE YOU ACTUALLY READING THESE POST?, BTW algae only grows (like fish and plants) when you have a healthy tank, alot of what your seeing is debris and not algae, the algae tablets you feed to your plecos etc is actually a "Dead" form of algae and not the kind that grows.
2, i have seen no comments about your readings of your tanks, do you even take readings, different species require different things. with all the mess those 3 now 2 bristlenose pleocs make i wouldnt be surprised if your ammonia levels were high.
3. I too keep clown loaches (they are so cool) and i have never had them be aggressive, maybe it depends on what other types of fish you have with them, i dont have betas,
4, People are telling you what to do without fulling explaining, IE Strata for example, some species of fish like to live in different depths of your tank, starting from top to middle to bottom, your tank looks bare because you have mostly fish (with the exception of the bettas and neons) that like to live on the bottom, you need to research fish that like to live in different layers of the tank, and that will make your tank look full,
5, back to test kits, you really need to get a chemical test kit API (aquarium pharmaceuticals inc,) makes a very very good liquid test kit, with all the fish your adding/removing i would be darned surprised if you havent had a spike or two, make sure what ever test kit you get, that it includes test for Nitrates, Nitrites, Ammonia, and PH, gh/kh would be good but not extremely important unless your having a hard time with PH fluctuations. PLEASE BEFORE YOU DO ANY THING ELSE GET A TEST KIT AND TEST YOUR TANK WATER.
As mentioned before this is not a self sustaining hobby, you need to do some work after all you are dealing with the LIFE OF A LIVING CREATURE and with that comes great responsibility.
6. And yes you ARE doing a great job with asking questions "the only dumb question is the one never asked"
5. plants, you definantly need more plants, some ancharis, swords and java fern moss are easy to grow, require very little light and you can get away with no c02 injections. also your fish will love you for it, especially cardinals and the loaches, they are very shy, and love hiding places, some nice rock caves or good grown swords would be perfect for them.
6, i read earlier somoene suggested an arwana, if thats the fish im thinking of, then (with all due respect) that person has no idea about them, they grow too big for your tank.
if you want to know more about a specific species of fish, then just GOOGLE it, you should really research each type of fish, specific needs, ie" its adult size (oh that reminds me, when people have told you that you are overstocking, it doesn't nessacarily mean right now, the ADULT size is what is most important, yes your loahes may only be 1 inch now, but in the wild they grow to be 12 inches, in most tanks they grow to be 6-8 inches, thats something to think about, ) type of food, Ph range that it prefers, temperature it prefers, and most importantly the aggressiveness and tank mates it can be companioned with.
Good luck with everything and please come back and let us know your test reults and whats going on
Kevin