Your tank runs on gear that fails quietly

Aim for four to six times your tank volume in turnover per hour for a community tank, and closer to eight to ten times for a heavily stocked or messy setup like goldfish or cichlids. A 200 litre community tank wants roughly 800 to 1,200 litres per hour. Bear in mind that the flow rate printed on the box is measured with no media and no head height, so expect real-world output to land around 30 percent lower.

The old rule of 5 watts per gallon runs hot for most homes. Around 2 to 3 watts per litre works if your room sits within a few degrees of your target temperature, so a 100 litre tank is usually fine on 200 watts. If the room drops below 18C in winter, size up or run two smaller heaters at opposite ends, which also means a single failure cannot cook or chill the whole tank.

Rinse mechanical media such as sponges and floss every two to four weeks in old tank water, never under the tap. Biological media like ceramic rings or bio-balls should be left alone for months and only swished gently when flow drops. Chlorine from tap water kills the bacterial colony you spent weeks growing, and a filter cleaned too aggressively is a common cause of a sudden ammonia spike.

It is, when it is controlled. Problems come from uncontrolled injection rather than CO2 itself. Keep your drop checker in the green, target a pH drop of about 1.0 from your degassed baseline, run the solenoid on a timer that stops CO2 an hour before lights out, and keep surface agitation running overnight. Fish gasping at the surface in the evening is the signal to cut the bubble rate immediately.

Usually not, but it is telling you something. A new hum after months of quiet running normally means an impeller has picked up debris, a bearing has worn, or an air pump diaphragm has stiffened. Pull the impeller and check the shaft for wear grooves first, since that is the cheapest part and the most common cause. A grinding noise, in contrast to a hum, means metal contact and deserves attention within days.