O2, Air Stones, And Air Pumps

[NewTankGuy]

[SIZE=10.5pt]I hear a lot about O2 levels, air stones, and air pumps, so I wanted to know how do I know if I need something like this for my tank?  I currently have a 29-gallon freshwater, lightly to moderately planted tank (depends on if you count only live plants, or live and fake), with a HOB Whisper 40 filter.  However, I have learned that my current tank is way too over populated, so within the next month, I will be stepping up to a 75-90 gallon freshwater tank to better accommodate the fish I already have.  So how do I know if I need to have this in my setup, or if I am fine without it? And if I should have this in my tank....where in the world do I begin to find out what I should have, and what’s a waste of time and money. As so far all the advice I have gotten from my LPS has been wrong, and borderline worthless (which is why my tank is way over populated as they assured me that “29 gallons is more than enough for this population”, and the only real pet store/fish store I have around is PSP….[/SIZE]

 

[Ch4rlie]

Your fish will tell you if you need more o2.
 
Fish gasping as surface of water could be a sign of not enough water oxygenation.
 
Basically, all you need is to have the tank water surface being rippled or being agitated, this is what oxygenates the tank water.

 

[NewTankGuy]

so basically no gasping fish, and a HOB filter, and thees no need for any of that stuff?

 

[Ch4rlie]

Pretty much yes, I have a HOB on my tank as well, no extra filtration or airstone at all.
 
The water surface is rippled by the HOB waterfall effect, make sure the water level is at optimum level for this, you're good to go basically.
 
You can add an airstone if you desire to, wont do any harm at all really.

 

[NewTankGuy]

So being new to aquariums, what is the "optimum level" for the waterfall effect with a HOB filter?

 

[Ch4rlie]

When you see the water rippling most from the HOB basically.
 
But does sometimes depends on why you plan to stock the tank with, some fish prefer slower flow so the ripples may need to be gentler or faster either by raising or lowering the water level.