Where are these bubbles comming from?

[Rickvn]

Hi all....does anyone have any ideas about this? I have run out of ideas.

I have a Juwel 180 litre tank with the built in filter box. I use this as a chemical filter. As media I have 3 course blue sponges which I was every week to avoid them going biological, some phosphate remover in filter socks (Rowa Rowaphos) and Rowa charcoal. I have pads of filter wool between the layers of material.

My problem is a day or two after cleaning the filter it starts blowing tiny microbubbles into the tank. I can assure you that the powerhead (Juwel specific powerhead - 600 lph) is totally submerged and there are no pipes or fittings required.....the whole box is submerged. So no air is being sucked in by accident. I even replaced the powerhead a month ago just in case somehow air was being sucked in down the electric cable...yes....I was that desperate!

So where can the bubbles come from? Can they be manufactured by some type of chemical reaction of the Rowaphos or charcoal? Sometimes they get really bad and it is a real pain to disassemble the filter every two days to clean it. I've tried soaking the charcoal in hot water to remove all bubbles beforehand. Rinsed everything in RO water.....I just have run out of ideas. My LFS can't come up with anything to explain it either.

I'd love to get to the bottom of this!

 

[eyring2210]

is the impeller for the powerhead clean and not damaged? The bubbles could be from cavitation.

 

[BigJim]

Why don't want the sponges to go biological? More filtration is always better.

If you're washing the sponges, I'll bet you're getting air trapped in the filter and they're just working their way out. When I do a water change on my tanks, I get air in the suction tubes of my HOB filters and it can take a few days to work itself out sometimes.

 

[Rickvn]

Hi Eyring & Bigjim. Thanks for your replies. I don't think either explain my problem.

Eyering...as I said, it is a new powerhead (including the impeller). The old one did the same thing. So unless the design of the impeller is causing the bubbles to form then it can't be the cause otherwise everyone using Juwel powerheads would have the same problem.

Bigjim....There seems to be different opinions on biological sponges. I started out leaving them to go bio on the advice of one of the guys at my LFS. A few months later I has phosphates building up and spoke to a different guy at the same LFS. He asked about my filter media and advised that I DO NOT allow the sponges to go bio and wash them weekly in tap water then rinse in RO water. I read up on this issue and there is a split in opinion. The reason for not letting them go bio is given that they become a nitrate trap....I dunno how....but this is what the second guy at my LFS said as well. There are arguments for both on these forums....I have read a few. So that is why I don't let them stay in for more than a week. As for washing them leaving bubbles...I don't think so. Firstly they are too course to trap any air. Secondly...they are at the bottom of the filter box and if I aggitate the top media (charcoal sock) a bit the bubble shower increases dramatically which indicates to me the bubbles are in the upper layers of filter media and are released when I move it. that is why I was wondering if the chemical process within the charcoal reacting with something in the water could produce bubbles. BTW...I have even tried soaking my charcoal in hot water before using it to remove trapped bubbles in it...makes no difference.

Thanks both for your ideas.

Any more ideas .... anyone?