Strange knocking???

[sundayangelmona]

(01-27-2011 08:50 PM)Lady Kamae Wrote:  I have pretty big fish, they are actually koi for our outdoor pond but since they are still rather young I brought them in for winter this year. They are also very loud, noisy fish that like to bang around and toss the rocks. River rocks too not just the little colored pebbles. UNR mentioned a fish could break an aquarium...with they way these koi carry on, I believe it!

Knowing how aquariums are set up though it makes me wonder what condition your filter or aerator are in. Does your filter need changed? Do you use the filter balls in addition...because they can rattle and bang around when they need to be removed and cleaned. I also wonder if the aerator might need cleaned...we have to remove and wipe ours down weekly. When the bacteria builds up on the tube and blocks the airflow it makes some crazy noises...hissing, whistling and even tapping.

So there are just a couple of possibilities. I'd suggest to do the tank maintance and see if the knocks settle down...and of course we are here for you, so stop back by and let us know how things are going.

Thanks for the possible explanation.But my fish are small.The largest of them is just 1 inch,they don't grow larger.I have an external filter so the filter is very quiet I don't even hear it.Also I don't have an aerator.I know that filter can make noise but not that kind of sound.It would be like somebody knocks on your window or something loudly.Dont know how to explain...Here is something similar:
http://www.soundsnap.com/node/12784

[dyingenglish]

if that was what it sounded like then i don't think it would have been a fishtank... The sound of someone rapping on a window pane has a sort of.... unstable sound where as a fishtank would be more solid. also, i don't care how fast a fish could swim there's no way it could make a sound that rapid. maybe something inside the part of the fishtank that cleans or cycles the water was thwapping against it. you know what i mean? the sound of plastic being knocked on probably sounds more like that then the glass of a fish tank.

[UglyNRude]

I googled fish tank knock and was surprised at the results.

Heater knock
Pump knock
Skimmer knock
Outside Filter knock

[sundayangelmona]

(01-29-2011 05:51 AM)UglyNRude Wrote:  I googled fish tank knock and was surprised at the results.

Heater knock
Pump knock
Skimmer knock
Outside Filter knock

But what kind of knock?The filter isn't even in the aquarium.It is connected by tubes but it is almost 2 meters away in the cabinet.Also the knocking was on the cover glass of the aquarium which is much slimmer than glass of the fish tank.Just like window glass.The sound came from outside the tank not inside because it wouldn't be so clear and loud.I appreciate that you are trying to help but nothing in the tank can make such noise.I remember that when I heard the first knocking I hoped that this was my dog on the aquarium trying to brake in aquarium.But than I noticed that doors are closed and that he isn't in the bedroom at all.And I remember that he was never interest in aquarium at all.But in my had that moment i hoped that is he.