Early on I did not allow pets and my tenant had a 100 gallon fish tank with fish.  

Hi BP,I just got a service call for a leaking filler valve, it was spraying in 2 or 3 directions and leaking down the tank, this is the first day of my tenant living here too.

.-  Medical collections can tank a score. 

I've done million dollar loans (not my money being lent) for people with 800 FICO scores that I wouldn't let borrow a pencil (if I owned the pencil) for fear that they'd steal it (but, again, if you want to pay me to lend someone else's pencil... sure, here you are).Conversely, I've had to say "no" to people that I would let marry my sister and lend my personal car to in exchange for a full gas tank with no hesitation, because of a stupid FICO score thing.As landlords renting out your own property that you actually own, you are strongly advised to throw out the FICO score and look at & understand their credit history. 

You are right no one trusts a landlord, Landlords are not a trustworthy segment of business society, akin to the loan shark business. 

Many times the plastic/rubber flap inside the tank doesn't close properly so the toilet runs and runs. 

Tenants who are the "complainers," can smell weakness like a shark LOL.  

The problem isn't the additional hot water usage, it's the undersized hot water tank.

I collected the keys off the table and told him as a matter of policy I treat everyone the same (he owns a construction business but had a bankruptcy and lost the MANSION of a house he was living in after the economy tanked and he filed bankruptcy) and don't exchange keys without first/last months rent.  

Or, I understand that an aquarium is good for your anxiety, but an 80 gallon tank is not acceptable, because it could fall through the floor.