also are those air flow limiting valves safe for the air pump to reduce the flow of air, I have one because the air bubbles are just way too many without one and it scares the fish away
a check valve is to prevent back siphoning of water into the pump if you have a power outage or unplug the pump by accident. I'd suggest checking it by blowing through it the wrong way; if air does pass through get a new check valve (check new ones to be sure they don't limit airflow too much, and that the close in the wrong direction, many are cheap crap and don't work the day you buy them, so check them before you leave the store with it...note: same with thermometers, compare them with each other so you don't get the one that's crap) what you want is a normal air valve, they come in various configurations, one or more valves so as to run multiple airstones and to balance the airflow to each stone or ornament. You should not however just use the valve to limit airflow, as this damages the pump eventually. You can just let one of two valves bleed off a little air; however make sure another check valve is in the line from the tank to the valves or else you risk water coming out of that valve if it's lower than the tank water level.....You may want a smaller air pump or an adjustable one instead.
