Bacterial bloom trouble shooting

mp2022 · Mar 17, 2025

Hi all. Trying to troubleshoot recent bacterial bloom.

My tank is about 6-8 weeks at this point and has been doing fairly well. It's 40 gallons or so. I have 2 clowns, yellow striped blenny, tessellated blenny, orchid dotty back, clown jester, watchman goby and assorted inverts. I have a mixture of soft and LPS corals. All seem to be doing relatively well.

My nitrates are 10, phos 0.25, alk like 8.5, ca 450, mg 1300 or so.

I recently added a 10g tank turned makeshift sump while I wait for a prefabricated sump I purchased. In this I transferred my HOB filter and protein skimmer, added a piece of new Caribsea dry life rock, and some chaeto algae which was sitting in the display tank previously. A day after I did this my water got all cloudy which I think is a bacterial bloom.

I am trying to figure out what happened and think it is probably from:

1) I had to add some additional water to the tank when I added my "sump" and I accidentally poured it in the sand bed quickly and it stirred up a ton of sand and probably detritus which probably caused a mini cycle.
2) Adding the new piece of dry rock to the sump started some mini cycle.
3) Some other reason

Any other thoughts? I guess nothing to really do about it but wait it out?

Thanks all in advance. This is a great community.

stE26wy14 · Mar 17, 2025

woooahhhh that is a MASSIVE bioload for that small of a span/tank. get a uv sterilizer, into the sump no more fish for a while. u got a tank pic? i wanna see :D

Subsea · Mar 17, 2025

How long has 40G tank been set up before adding the 10G sump.?

mp2022 · Mar 18, 2025

Subsea said:
How long has 40G tank been set up before adding the 10G sump.?

6 or 7 weeks - I decided to make a move to the sump for a dedicated refugium and increased effective water volume.

I added all the fish over the course of a couple of weeks from the time I set up the tank so they have all been in there a month. Yes quick addition of livestock - probably a bit overeager. I set up my tank with dirty water, live rock, and sand I got from the tanks from this local coral aquaculture store (in an attempt to transplant their system into mine) and the tank has had stable parameters with nitrates ~ 10, ammonia/nitrite 0 for a while now. I had an algae problem up until recently which was probably due to too much light exposure which has abated with significantly lowering my light intensity and duration and the addition of a decent cleanup crew. My phosphate had been 0 up until a week or so ago which I attempted to correct with heavy feeding, which may also have contributed to the bacterial bloom. So I think all in all my tank is probably not completely cycled but is hanging in there.

That being said, this morning the tank is much clearer so it seems to be sorting it self out...

Thanks.