Foam in the sump, white froth.

I have a plumbed tank for my axolotl. He resides in a 55 gallon approximately 2/3 full. The refugium, filter and sump are in a 20gal Long under the stand.

Refugium is about 10gal and has blind cave tetras and a few mollies along with some fast growing plants (anacharis, etc). Photos are posted in the gallery. Four days ago I began CO2 in the main tank but due to my pH and kH I am only at 15-20 ppm.

The last two mornings I have noticed a surface corner of my sump built up with something frothy, like whipped latte topping. I am hoping this is a good enough description and that perhaps this is evidence of bacteria growth but I don't know how to test for anything beyond water chemistry.

Filter trap consists of: rubber grate, sponge, active carbon (changed every 2 weeks) and in the upright chamber more rubber grate folded in on itself for bacteria colonies.

Do you use dechlorinater? Some can leave a foamy residue, make sure you are using the correct amount. It could also be a bacterial bloom. It could also just be protiens from fish waste. What are your water parameters?

Did you cycle the tank and sump? Is it set up to cope with the high bioload that you have?

I could be wrong, but was under the impression that it wasn't good for the axies to be kept in a co2 tank. Fish have scales to protect themselves to some extent from the co2, axies don't have the scales and have permeable skin and will absorb it. Plants that require c02 also demand a higher amount of light, axies get stressed if there is too much light. Have you thought of going low tech? There is a large list of plants that can survive without co2 or demanding too much light.

Sorry for the essay, it is meant in a helpful positive way - sorry if it doesn't read as such.

Thank you very much for your lengthy response, I take no offense at all and will read all comments as helpful and with the best interest of my axie in mind.

I do not use dechlorinator as I live in a rural area and take cool hosewater (pre-softener) straight from the hose to do my water changes. My water parameters are slowly changing as I am trying to work down my pH slowly. Currently I am at:

temp 64-66F
pH 7.8 (target is 7.4)
gH 250ppm
kH 240ppm
ammonia 0
nitrite 0
nitrate 5ppm
CO2 (by calculation) 16-18ppm

My tank and filters have all cycled and have been running for approximately 5 weeks now. With just start-up fish (which I didn't discard, they are still in my refugium) and before my axolotl went into the main display tank I ran a sponge and an ammonia reducing media. After 3 weeks when the media went brown I added active carbon and a week later removed the ammonia reducer. Sponge filters are well aged and have cycled as well. I saw the initial Ns spike and then settle back down to next to nothing before I put in my axie.

Flow rate on my filters and pumps is hard to estimate as I have a gate valve on my return line restricting some flow. It is a 280gph pump, moving approximately 60gal water. To keep flow to a minimum for the axolotl I have it dialed just enough to move debris which doesnt seem to bother him and near the bottom back of the tank. Main display water column moves over and up until it meets the overflow at the opposite end of the tank. Surface movement is completely non-existant (though I am considering a small airstone timed to come on at night and aid in Oxygen exchange).

My lights appear very strong due to their K rating but do not have output comparable to anything high-end. My plants are medium light and did fine without CO2 addition. I went with the DIY CO2 for purposes of light cycle. At 12 hours light (10 hours full, with a 1 hour dawn and 1 hour dust) I was getting some algae growth. I stopped all plant fertilizing, reduced dayligh to 8 hours full with only a 30 minute dawn and dust, retimed refugium lights to be opposing the main display (no dawn/dust there). Because LED do not compare easily to other lights in watts I know this wont mean much but they are 9w (3x3) 5000k & 9w (3x3) 6500k floods, placed in reflective domes 24" above the tank which is about 30" above the water line.

Tech-wise, I realise my tank system sounds elaborate but considering a computer program monitors and controls these parameters it is actually only as technical as it needs to be. Effects like 2% at a step, gradual increase light output from 0-100% over an hour each morning to me is worth it, as is 'natural' tank cooling using a chilled water resevoir to my rain bar placed above the tank. CO2 at this time is simple and DIY to get some strong growth from a few of my weaker plants before my axie uproots and shreds them completely before they could establish themselves. I had not considered amphibian tolerances being lower than scaled animals however and will definately do some research into that. Typically ppm in a planted aquarium can go as high as 30-35ppm for fish (so I read) are you suggesting there is no safe CO2 level for amphibians or that their tolerance is lower?

Thank you again for your comments, I am seeing this morning the "froth" much more spread out along the corner of my sump where it had been for the last few days 'stacked up' into one corner. I did simulate a gentle rain overnight last night so in figuring out what I have going on here it may be important to note that I had some overnight surface agitations, up in the main display.

I have narrowed the source of this 'froth' to either excess plant material in my refugium or (less likely but more hopeful) a bubble nest being pulled through my filters and surfacing in the sump.

I did a complete vacuuming of my substrate and found more in the refug. than I like to admit. Next major cleaning I will add a UGF to the refugium w/ a power head blowing down. Doing this will allow me to move my diffusion chamber to the 20L, and hopefully get more anacharis shed up and into the filter trap than I am now.