Weird black silt in one of our closed systems

Sarah McAnulty

Larval Mass
Hi Tonmo!

I'm in a lab raising bobtail squid and in the last 4 months we've started to get this VERY strange black sooty looking stuff in only our egg nursery. We've also noticed that clutches in the nursery have been hatching very poorly but when we put them in our other 4 systems they hatch perfectly normally. We make our seawater from instant ocean, it's not carbon dust, and I only 1 of our 4 systems has it. I'm wondering if anyone has seen this before and what they've done about it?

Anything that enters the water gets the black silt

What bioballs SHOULD look like

What the nursery's bioballs currently look like

Any advice would be appreciated!



Hi Sarah,

We also get some black encrusting growth on some of our airlines (but not on bioballs). I think it's bacterial, maybe some sort of sulfurous kind, but I haven't seen it affect hatching success of our bobtails (although we have all sorts of other problems raising them!). We've reduced the growth of it considerably by adding UV skimmers (maybe check/replace your bulbs?) and by reducing our PO4 load. Do you test for phosphates?

Good luck!

Sarah McAnulty

Larval Mass
It doesn't smell strongly, but I admit I haven't stuck my face in and taken a good whiff (I can do that tomorrow when I'm back in lab).

We have UV bulbs, and we replaced all of the carbon, the filters, the bulb thinking that might help but nothing helped :/ But I haven't checked for phosphates, though I can check on that. I'll try plating it tomorrow to see if any bacteria grows. Thanks!

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