I was given a new Snowbee smoker for Christmas. I have smoked fish before but it was a few years ago. I have recently been trying to smoke some Kahawai fillets and have had a terrible run with several batches ruined due to an extreme bitter taste in the fish. I'm using Manuka if that assists with solving the problem. Initially I thought I had just overlooked the fish, then I thought I burnt the wood chips, now I'm thinking I have two much heat as I have two burners in comparison to one like I had on the old unit (which I didn't seem to have any problems with). Any help would be appreciated as I have another batch of fillets in brine tonight which without assistance I will no doubt destroy tomorrow. Thanks

If its a 2nd hand smoker, make sure the lid is not all blackened up with gunk otherwise it can drip on the fish, wash lid in a degreaser/detergent or waterblast it.

too much smoke? if i use too much fresh thyme in my wood smoker the fish has a more bitter taste

ruined due to an extreme bitter taste in the fish. I'm using Manuka if that assists with solving the problem.
I cold smoke... started with manukau and basic methods and refined over the last few yrs...
The biggest refinement was NEVER to use manuka again....it gives a harsh edge to the finished product.
The other thing that will do this is if the wood chips go from wood to charcoal then are allowed to turn to ash.....NEVER allow ash to form

I now use blends of apple, cherry, pohutukawa, a little hickory  .. the blend very much depends what is on the shelf and what is in the shop at the time.

Get the wood right, from there u can then experiment with amount of salt, type brown sugars, molassis, rum / brandy, pepper and chilly sauces (not for the heat but background chilly flavour) etc

The biggest way to 'improve' your 'product' is not to ask people if they like it... but ask them "what would make it better"

As others have said: It's likely to be too much smoke, or iodised salt

I think manuka is a lovely wood to smoke with.

If you're still having issues after tomorrow's batch then do the next lot as simply as possible - i.e. no brine, just rub soft brown sugar and sea salt onto the dry fillets and then smoke them. That approach will eliminate anything you're putting on the fish and will help you focus on your smoking method

Yup. Use salt that hasn't had iodine added to it

Personally , from personal experimentation and a good basis of chemistry, and the concentration (rather lack of concentration ) iodine makes no difference at all.
If it did then it would effect other 'cooking as well.
Also up to the 1980s it was impossible to buy salt without iodine....by law, and since this legistasion was changed NZ has gone from a near zero goutier issue to increased numbers.
I have also experimented with other salts such as the pink Himalayain

Early heavy smoke... Again a lot of experimentation, I have found that having an initial higher temp which results in  heavy smoke, as the fish goes in... drys and seals the surface  (like searing a leg of wild venison before roasting) holds the oils and moisture in and aids in better colour espec when using mild flavour woods such as cherry , apple, pear. As the fish goes in the temp is turned down , but the heavier smoke lasts far longer

Another 'mod' I have made is no longer rub salt in, but rather 'set' the meat using a brine soln....BEFORE the smoke... same principle as a ham or bacon is 'set' before smoking. At this point I also add flavours such as chilli, rum, Brandy, molasses.....The fish after a 2 hr soak, is removed , patted dry and as small as possible quantity of malt brown sugar rubbed evenly over the surface.
Cooking/ smoking/ preserving is all about chemistry...
The 3 critical things in the basic flavour are the wood type, the amount of salt and amount of sugar.
Ie how salty it is.. espec when later used in fish cakes and pie.
And how sweet... does the sugar add to the fish flavour.... or more like putting 10 teaspoons of sugar in a cup of coffee ...
Same goes for things like chilli... do u want it to taste like a chilli picked off the plant with a fish texture, or have the fish have the background taste of chilli without the heat and still taste like fish.
And when put in a pie do you want it to taste like a smoked FISH pie or no different than if use something like toffu, salt sugar flavour smoke it and put that in the pie and taste the same.

you are probably using too much dust half a handful is all you need in those stainless meth's smokers do not be tempted to cover the hole try with dust it will only make the fish bitter
I run my smoker at about 70c I can just touch the racks with out getting burned takes anywhere from 1 -6 hours depending on the thickness of fish I use a mix of 3 parts sugar and one part salt then rinse and dry as per this vid

i use this exact method

another good trick with the meth's smokers is take the plates off your bbq and sit the smoker in the burners instead of using meth's it gives you much more control of tep

in-fact I am in the middle of smoking some snapper now I gut the snapper then take a fillet off one side which leaves you with a fame with a side still attached which is what I smoke the fillets I take off are skinned and boned and eaten normally gives you smoked fish and dinner off the same fish with no waste

how about this
cut a slot in the smoker were I put the black mark.....


and buy one of these


they are cheep as chips then simply put the smoker on top with the control knobs coming out trough the slot this will give you 100% full control of the heat

Similar to the above.. even the big ring requires far too much LPG to keep lit.. and evwen then with a modified regular.. slightest puff wind goes out.
I now have a 60mm diam hob burner that can cold smoke reliably down to 46/48 Deg

Several issues determine temps
1/ the exit vent, bigger the vent the lower the temp u can get...down side too big and most the smoke rises too fast, doesnt 'hang' and stuff doesnt get good even smoke contact thru out the whole smoker
2/ The flame size
3/ The water tray.. a MUST...the extra moisture this provides over and above that produced by burning meths or lpg acts like a buffer giving stable temps... even well over 120 deg C.
Also it an effective safety measure, the fats drop into the water tray rather than on the bottom... fat dropping on the bottom can ignite, burn....

Even with my cabinet smoker and the little 60cm burner I have stable temps from just below 50 degs right upto temps to cook a roast lamb as a oven....it is also ideal for keeping trays food hot when we have events here.