Bubble King 400 internal issues

flying Jock

New member
Hi everyone,

well after 30 years in the hobby I’ve decided to swap my old Tunze and Deltec skimmers for a BK 400 internal skimmer.

the build quality is far superior to any skimmer I’ve seen before.

the skimmer has been set up to run on a heavily stocked 1200l reef with fish fed 4 times per day.

I know the skimmer is rated at tanks larger than this but I’m due to upgrade in 12 months time to a 3000l reef.

the reef has been running around 7 years.

since adding the skimmer(3 weeks ago) I am really struggling to get any consistent skimming.

it constantly wet skims then overflows at a fast rate.

I have initially set it up in 235mm of water, which after advice I’ve raised the skimmer so it now sits in 200mm of water.

the skimmer has been set up with the telescopic tube lowered to its lowest setting and it is fully open.

the water inlet nozzle on each pump it’s screwed right into the pump body as if I turn it out the skimmer overflows more.

I could raise the skimmer more but then the top of the pumps will be out if the water and I’m concerned about them overheating and also producing swirls as they take in water.

the pumps pull air direct from outside on a 2ft air line.

one pump is connected to an ozoniser and the other pump is not and this line is blocked off so it does not pull extra water in.

I’ve read so much on the skimmer and where I might be going wrong but I’m lost as ti why it will not settle down and produce a consistent foam.

I do not add additives or anything that would upset the skimmers ability to produce consistent foam.

my Deltec and Tunze skimmers were producing great skimmate and running perfect prior to removing both for the new BK.

any help would be massively appreciated!

many thanks



RC Sponsor
Premium Member
You will NEVER get consistent skimming with that skimmer of a 1200l display. It’s WAY to big and you couldn’t possibly have enough fish to generate enough dissolved organics to generate enough foam to keep the neck of that skimmer consistently full with foam. It’s the proteins/dissolved organics in the water that allow bubbles to bind together into chains that form foam. In the absence of enough dissolved organics you will make bubbles and not foam. The bigger the skimmer, the larger the neck volume. Bubble Kings are conservatively rated and oversizing them will usually result in inconstant skimming. The skimmer will skim well for a day or two then slow down for several days or more until the organic levels build up enough in the water for the skimmer to make enough foam to fill the neck. Then it will skim well again and then slow down. Our size ratings at the low end of the range expect a heavy fish load. A heavy fish load is 1 cm of fish per 3.7 liters of display water. Not total system volume. Bottom line.. For that size display, I would have recommended a 250 size skimmer ONLY if you have a truly heavy fish load. In the absence of a heavy fish load, a 200 sized skimmer would have performed better but a 400 sized skimmer would never work well on your current system regardless of the fish load.