Bacteria Bloom or modern filters and gravel?

Question
From a scientific perspective: My hypothesis- something is different from the 80's to now that is causing many new tanks to cloud up.
When I was growing up, I had three fish tanks (no heaters, no chemicals, and the filters and filter media were different). I added tap water directly to the pond and tanks (that contained goldfish, tetras, and other topical fish) and they thrived without any chemical treatments. I even added sand from the ditch behind my place to a tank containing Swordtails and they multiplied like rabbits (over 30 three to four inch fish in a 10 gallon tank with no problems!), and the goldfish and Coyfish in the pond also multiplied and thrived too. Excluding variables like the heater in my current tank and chemicals to remove chlorine, waste, and amonia, what was different between fish supplies and tanks back then and now? Two things I have noticed is that the gravel is now larger and painted and the filter media is made of different materials. I never had any bacteria blooms back then but I do now- do you think that the paint on the larger gravel that is being sold now could be causing this, or the filter materials? I would like to hear your opinion and other peoples' out there to try and find a remedy to this common current problem that did not seem to exist back then and before the 80's.

Answer
Well, I was not born until the 80's so I do not know much about the previous conditions of aquarium equipment but I do have some ideas. For one thing the declorinators these days have things which no tank needs. For example, many say they have "beneficial bacteria" this to me is a big problem and causes excess coudyness and waste in the tanks, especially new ones. I have tested this by using a declorinator with and without the bacteria and I have discovered that the basic declorinator without any added stuff does not tend to cause cloudyness. However, if you use too much declorinator of any kind I also noticed that causes cloudy water. As for the gravel, I do not think the paint so much can cause anything but the lack of washing it properly can be a problem. Also, most pet stores keep thier gravel and sand in places near the tanks which in turn creates humidity which seeps into the gravel and sand and starts to breed mold and other bad bacteria, which causes a hugh problem once someone tries to run a tank with it. However, a simple solution to this problem is washing, washing, and re-washing out the gravel or sand before you put it into the tank. As for the filters, I think the current filters are only good developments for the fish tanks. If anything, the filters do way more now to clean and filter the water due to new technology and scientific discoveries. I hope I have given you some insight and helped alittle. I hope my reasoning makes sense. Oh, I almost forgot, today with increased polution and waste from humans, getting items from the backyard or outside without sterilizing it can be hazordous. In the 80's and before pollution and waste was beginning to be a problem but not nearly to the degree of now. Hope I helped.