Mystery of the knocking tank
I am hoping you can help me solve this mystery.
For the past couple of days, my wife has been hearing a strange knocking sound coming from our tank, like someone tapping on the glass. When she told me about it, I became concerned that the sound may be the precursor of some nightmare water disaster, so this morning I tried to hear the sound myself.
And yes, I did hear the sound. And she is correct -- it sounds just like someone tapping on the glass. I turned off the filter. The sound remained. There are no moving parts in this system except for the fish and the filter. I haven't added any new fish in months, so if it's the fish then it's new behavior.
The only thing that I have been doing differently is overdosing Excel to solve my algae problems.
But I tried to watch for the fish bumping against the glass or the heater, and I didn't see anything unusual.
The scary thing is that it sounded like the glass was starting to crack! There was a knocking sound, followed by the faint sound of cracking glass.
But there is no crack that I can see, and no water leaking.
Anyone ever had a problem like this?
Help me solve the mystery!
My fish inventory includes Bosemani Rainbows, zebra danios, neons, ottos, and an Ancistrus. I suspected the ancistrus because he's so clumsy, but I don't think he's responsible.
Methodology: Walstad Natural Style. No filter, No heater, dirt substrate with sand/gravel cap, two powerheads for water movement.
Tank: 40 Breeder
Lighting: Finnex Planted Plus
No CO2, but dosing Excel
Ludwigia (unsure what type), DHG, Hydrocoytle Tripartita, White Cloud Minnows, Blood Fin Tetras, Amano Shrimp, Nerite Snails.