Adrienne

Update:  As of yesterday my readings on the tank had settled.  A 10% waterchange was done using NSW and a largish leather mushroom with galaxy star polyps growing on the lower stem was added.
This morning two blue chromis were added to the tank.  Now I sit and wait

If you continue to do regular largish water changes ie 40-50% your cycle will still be going and that will be why you have zero nitrates.  You are correct 'now with the nitrite spike I wonder if the cycle is not complete'.  Nitrate tests are a precise thing, if you do not follow the instructions exactly (and I am not suggesting you are not, but the lfs may not be) then you will not get an accurate reading.   Bristlenose are the biggest waste producers ever and your tank is a bit small for even one - they will keep your cycling going.  Unfortunately nitrite, as you know is toxic to fish, prime will help lock it into a non toxic form but you will still get readings.   Your driftwood will help lower your pH.  Fish can adapt to higher pH readings, but are less likely to breed.  Swinging pH is far more damaging than pH that is stable but not where your fish prefer it.
My recommendations:
Try changing 10% daily or every couple of days, continue with prime and nitrozorb (it does work) and do as you are doing, keep an eye on your tank readings. 
Don't add any more fish or plants until it is sorted.
It takes several weeks for a tank to complete a cycle (depending on how you do it).

Yes good choice i have changed over to all Jebao now, variable speed is handy and service from these people has been outstanding http://aquarays.co.nz/

Salmon19 is trade me not this forum.
Caserole hasn't activated his membership on this site.

Thanks, I messaged Salmon19 on TM, fingers crossed.

Awesome tank.  That piece of wood has handled it very very well!

Welcome   A good rule of thumb with discus is one mature discus per 50 litres.  That is for a species only tank.  Less than 5 discus can be risky though as generally the odd one out will be picked on by the other two.  More so when they are mature and if you have a pairing up of two of them.  Discus, if you haven't kept them before are best purchased over 6cm in size, which should be around six months old - if they have been well raised and are healthy.  Younger and smaller than this they are a lot of work and don't do well in a planted tank.  There is a lot of rubbish discus out there so make sure you choose fish which are good colour, good round shape, not hiding at the back of the tank and ask to see them eating.  If they spit the food out I recommend you walk away from the whole tank lot.
Cardinals look spectacular in a discus tank particularly in numbers - I recommend a minimum 10.  They also handle the higher tank temps which are needed to keep your discus healthy.  You have clearly done some research - when I looked at the list the Kribs were really the ones that stuck out as potential problems if they pair up to breed as they can be highly territorial and often only one parents raises the fry, having given the other parent a beating.
I don't really know enough about elephant nose fish to comment.
Longfin BN are spectacular - my personal observations are that adult BN tend to struggle if tanks get over about 28 degrees.  I kept them in my discus tank, the fins did tend to get a bit torn on the driftwood.  Try and get two males rather than a pair as males are pretty rough on the females once they mature.  If they do breed you would likely have to remove the young as the discus will pick them off.
Filtration is a good topic.  a minimum of 4 x the turnover would see you requiring around 1200lph minimum.  It is important to keep the airation/water movement up in any tank and more so at higher temperatures.  With a heavily driftwood/planted tank 4 x is unlikely to get through and around the wood/plants giving dead spots which is where waste will accumulate.  Options would be to get a larger single filter - I would recommend around the 2000lph or a second fluval filter.  My discus tank was 450 litres and I ran an FN5 plus a Sunsun 1400lph filter on it and 2 powerheads to keep the flow circulating.  UV - anything over 24 watts is a steriliser, under is a purifier.  A slower water movement through the UV sleeve is needed for proper sterilisation as the water has more contact time with the UV light.
Regarding disease - you are best to quarantine all new additions for at least four weeks.  Less time and some diseases won't show themselves.  Four weeks and they should.  
Would love to see photos of your set up when you get started, progress reports with pics are always welcome.
 

Welcome back   It's been a while.

I have someone interested in this. He needs to clear it with his wife one last time. Their first fishtank for the kids .  

Looks incredible! Good luck and can't wait to see it with the fish :-)

The majority of the time, surface area ("Footprint") is considered a major factor for fish. This will affect the amount of fish that can live and compete in one area of the tank (eg the number of bottom dwellers you can have). Volume is important for a variety of reasons including water quality, but Footprint is essential to prevent overcrowding and aggression (unlike us, fish can't move up a floor when annoying neighbours move in).
 
I would personally suggest perhaps getting two more Otocinclus - these guys are found in the thousands in the wild (and are predominantly wild-caught), so the more the better  

Thanks!
I'm pleased you think that about the hardscape, I've been halfway in the tank trying to make it appealing for the last two months ha ha. I sit and wonder what to shuffle next. Who even needs TV anymore? 
There is actually a window right next to the tank, so I did sort of anticipate a bit of extra algae growth from that. It's been going through some weird changes lately but now that's all that remains. No more stringy brown algae yay!!

The algae on the glass is being caused by too much light getting to the front of the tank - could be indirect light so coming from a window across the other side of the room.  It looks very very good - your hardscape is beautiful imo and the plants are coming along well.

Thanks for the heads up Adrienne. I've heard of Ron having very good discus. Time to do a trip to the Shore this weekend.

Still relatively new to marines myself (16 months) so I can only offer a small amount of advice but yes, you are not the first person to adapt a tank.  In fact, if you go to HFF Albany they have a Juwel tank converted to a marine which runs through a cannister filter.
I believe you can get HOB (hang on back skimmers).  If the tank is new and you cut it you will cancel the warranty on it.  The overhead filtration that comes with the tank is not suitable for a marine tank.  You could look at putting a sump in the cabinet but you do not have to have a sump.  People do do it by removing the majority of the centre partition, slotting the sump in and then replacing the front part of the division for bracing.  
The standard T8 tubes will not provide enough light.  The 980T is relatively tall and insufficient light will get through - you would need a minimum of T5 lighting for corals, even the easy care ones.
On the fish front mandarin or any dragonets require a tank that has been running for a minimum of 12 months.  Their food source is live copepods and the population of these needs to establish properly in order for them to thrive.  I have a copperband butterfly in my tank - it is 250 litres.  Once again they are a very difficult fish to get to thrive.  Personally I think the tank is too small for a tang but I know others will disagree with me and some keep them in tanks smaller.
Hope that helps a bit

While we were going a bit made waiting for it to clear we took off all the panels we had built, painted them and made a hood for it. It was at this point I was beginning to feel a lot happier about how things were going.

Today the wire was run up the bedroom wall, through the ceiling cavity and down the lounge wall into the hall cupboard.  The photos show it all
Hole lounge side (sits just behind the tank)

Power points in place in hall cupboard (backs the lounge wall)

Lounge side with labelled cables for tank equipment

Hall cupboard side with plugs in sockets - all labelled.  Lighting box currently sitting on the carpet but will be placed on the wall.

and the tank from the front

 

Hi
Reef tanks are expensive (there is not point in saying they are not)  unless you go something like FOWLR - fish only with live rock (no corals) and even then the equipment you need is costly and they are time consuming.
The sized tank you are looking at is not a bad size but if possible it would be better to go deeper ie 120L x 45H x 60D.  This is because in nature reefs don't exist in the lower levels and corals need decent, although not always high light.
Considerations re equipment for a tank that size
Sump - with return pump 
         - with skimmer
         - with heater
 Wavemakers - will be needed depending on the pump size, hardscape and types of corals
 ATO or ATU - automatic top off or top up (called either) as evaporation can be high
RO/DI unit - essential if you are going to use tap/tank water, not so necessary if you are using NSW - natural salt water but the water around NZ has salinity of 1.027 and tropical marines are 1.022 - 1.025
Refractometer - to test salinity
TDS meter 
Lighting - once again depends on what you are keeping.
Are you thinking of tropical marine - or local marine (marines found in NZ waters)? 
If local marine you will require a chiller.
Fish - the best bit of advice I was ever given was decide what you would like and check out compatibility before you purchase the first one.
Corals - there are 'beginner' corals out there.  I can assist with some 'easier care' frags to start you off.
I am not going to tell you to research as I know from experience that you spend a lot of time doing research
Patience, heaps of patience is the key.  If you get impatient and think 'oh I am sure it will be okay' then trouble will likely happen.
 
My big tank in the lounge - the one you saw empty is 150L x 60H x 50D - not the ideal height (lower and deeper would be better) but will give you some idea of the size yours would be.
As far as sumps go - go as large as you possibly can.  Sump design varies but if you look at my thread on here 'and so it begins' you will see the sump that was designed for me.  NB the 'square' part of it on the right hand side, slightly higher is the ATO storage.  My other marine has a plastic food grade barrel for storing the top off water.
Once again, you are welcome to come and look and chat specifically about the marine tanks.  I don't know it all and never will but I can put you on to people who will give you the right, and good advice.
Good luck
 

You can also get adapters that clip onto a sink tap from Miter 10, the warehouse, bunnings etc.  Just siphon from the tank out the door, connect to the tap and fill it back up.  Dump some stresscoat in the tank beforehand if you want.

Today the wire was run up the bedroom wall, through the ceiling cavity and down the lounge wall into the hall cupboard.  The photos show it all
Hole lounge side (sits just behind the tank)

Power points in place in hall cupboard (backs the lounge wall)

Lounge side with labelled cables for tank equipment

Hall cupboard side with plugs in sockets - all labelled.  Lighting box currently sitting on the carpet but will be placed on the wall.

and the tank from the front

 

Excellent - that will be an amazing read.
 

Please be careful and make sure you are catching guppies and not gambusia, which look very similar but are a pest fish and illegal to catch.

Today the wire was run up the bedroom wall, through the ceiling cavity and down the lounge wall into the hall cupboard.  The photos show it all
Hole lounge side (sits just behind the tank)

Power points in place in hall cupboard (backs the lounge wall)

Lounge side with labelled cables for tank equipment

Hall cupboard side with plugs in sockets - all labelled.  Lighting box currently sitting on the carpet but will be placed on the wall.

and the tank from the front

 

It has been confirmed by my son in law, a registered sparky, that the loading this new setup is going to place on the circuit that runs to the sockets behind the tank - is going to more than overload it.  Therefore this week he will be running cables through the ceiling from the circuit the master bedroom is on to enable the tank to operate.  We have worked out that it will use a minimum of 6 amps at any given time.  The hall cupboard sits around the corner from the tank so the new power sockets will be put in the cupboard and the multiplugs and light powerbox will also be in the cupboard.  A hole will be cut in the wall to run the cables through and then a small cage placed over the inside of the cupboard to prevent any plugs being knocked when the vacuum cleaner is taken out or put back in.  I will take photos of the progress if I am here when it happens.  
We can not add to our existing switchboard (if anyone was wondering why we just don't do that).

On Tuesday my lights, skimmer, pump, ATO and 2 x powerheads arrived.