COVID AND THE VACCINE - TRUTH, LIES, AND MISCONCEPTIONS REVEALED, page-39018

My pleasure.

The only way a rat would get into the system is from the gutter or through the drain when the cap is off. Even then the leaf basket will stop them actually getting washed into the tank water and they would be long dead by that stage so just a treat to find.

If you have a system installed and can get the tank close enough to the gutter source just feed the pipe/s in above ground with a fall to the tank, then you only need clean the gutters and leaf basket. If it's too far away then go down underground and back up with a T piece at the lowest point to somewhere low enough to drain the system dry by unscrewing a cap.

When my tank is full I drain down the systems feeding it and then put the caps[3] back on just enough to keep them in place and any curious creatures out. That way, when it rains the caps just pop off and the water can drain away.

With no light there can be no bacteria but any leaf litter will break down and become sediment, giving off a bit of gas in the process. That will stay undisturbed unless you let the level get really low and the flood coming in stirs it up but it soon settles again and is more inert than it was. Best not to stir the water. Imagine all that crystal clear pure water deep underground with no light or movement most of the time. That's what we need to copy.

Gutter guard has it's problems because fine particles still get through and line the gutters causing corrosion over time and you can't clean it out.

I use a leaf blower most of the time which is fast and effective. Once a year I clean them out thoroughly using a hose and a toilet brush which is ideal. A bonus is that your gutters will last much, much longer as a result.