is my external filter turning over 400 gph efficient enough for my tank its a 125 gallon with 4 reds how do u work out what the gph should be for each tank is there a simple rule? i have cloudy water so was wondering if my filter is not enough
Of course high gph doesn't necessarily mean "Good filtration," there's other aspects to filtration than gph.
However, to answer your question, I usually like to have almost 10 times the volume of the tank turning over per hour.
For example, I have 1,300 gph turning over in my 150 gallon, 500 gph turning over in my 54 gallon... etc.
A general rule of thumb is turning the volume of water over 5 to 6 times an hour. But in my opinion this depends on what type of filter or how stocked your tank is. For example on my 125 I have 2 XP3's. This is almost sufficient for my overstocked community tank. I still have to do 25% water change every week. What kind of filter do you have on your tank? How much bio media do you use? This will help us to tell you if your fish will be all right or not.
i am just thinking that it wont hurt even if all the filteration isnt needed more than less is surely better. i want my tank water crystal clear like my old tank but my reds are nearly twice the size now