State of the art ULNS


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Coral reef aquariums have come a long way — and few examples demonstrate the current level of excellence as well as this. Jeremy Gay praises the work of Polish reefkeeper Krzysztof Tryc.

Clean, pristine and full of fish and SPS coral colour, this superb 160cm/63” tank must be the envy of many.

It has been set up for some six years and shows off what can be achieved with the right knowledge, equipment and methodology.

It uses several in-vogue methods, including the Ultra Low Nutrient System, or ULNS, using special zeolites and bacteria dosing to tightly cycle nutrients, and the Balling method of liquid supplementation to precisely deliver the minerals the corals need to build their skeletons and make sure that they are always available for growth.

Current trends

PFK have been studying these two relatively new methods for some time, as many greeted them with scepticism when first launched.

“It’s not natural” said many, “and its not long term” — though a growing number of hobbyists around the world are getting stunning long-term results when using them.

So what does ULNS achieve? In short, stunning SPS coral colours, which may even be more vivid than those in the ocean. The colours in these images here aren’t Photoshopped or doctored in any other way. They actually are that colour!

Take away all the organics from a captive system and corals show much better colour. Go Ultra Low Nutrient and they may turn out like these stunning examples, which, instead of being cloaked in brown zooxanthellae, are showing bright blues, pinks, purples and yellows.

To really show off ULNS coral colours, combine with multiple T5 lighting and, if extremely lucky and a very good reefkeeper, you may end up with something like Krzystyof’s stunning creation.

Why we like it...

The colours of this tank’s corals impact immediately and even our non-fishkeeping magazine designer said: “I can’t see the live rock.” This is highly relevant, as on a proper reef there won’t be any bare rock. It should all be covered in corals and other inverts.

It’s great to see SPS just kept with other SPS and the visual results are very contemporary, yet more representative of a particular zone on a natural reef. Add Green chromis, Anthias and a fine selection of tangs, as Krzystyof has, and we think this tank is near perfection.

Lighting and flow are powerful, as expected with an SPS set-up, but again, with multiple T5 lighting designed to enhance coral colours, this tank reflects the trends of the moment.

The skimmer is typically oversized and not cheap, at some 1,000 euros/£880, though it is the heart of the system and mega skimmers are enjoying a revival after many hobbyists tried skimmer-less, algae-based refugium systems. Skimmer design is better too.

You won’t get a system like this without a good skimmer and without control, and the combination used here ensures stability from control - essential when keeping SPS.

We decided to ask Krzysztof some key questions to find out how he came to create such a beauty.

Did you have any tanks before this one? 

My first was set up in 1996 and had many soft corals and a few LPS and SPS corals.

What differences did ULNS make to your system?

It’s much easier to achieve more brilliant colours, more transparent water and really clean rocks.

How did you introduce ULNS?

Before starting the Zeovit method I tried various methods and never had real trouble keeping low levels of NO3 or PO4 . That’s why switching to Zeovit didn’t cause any shock to my system. I didn’t follow instructions critically, but adjusted doses of products to the needs of my tank.

Would you recommend ULNS to other hobbyists?

Yes, but with care. Before starting I read much information from the Korallen-Zucht Zeovit forum. I was well prepared.

As for anyone having problems with the ULNS method, I’m convinced that if they have they are caused by overdosing, changes being made too quickly - or just through ignorance.

Does T5 lighting make a signficant difference and did you use metal halide lighting prior to that?

I used to have metal halide lighting in conjunction with my T5s. Although I liked the shimmering effect of metal halides, with T5 you can more easily adjust colour by swapping one bulb for another. Additionally, all corals are lit more steadily than under metal halides.

However, I feel you can get a good growth and colour of corals under both metal halides and T5. Maybe one day I’ll come back to metal halides along with T5!

Some of your corals are quite large. Do you have to frag them regularly and what do you do with those frags?

Space in the tank is limited, so I have to frag them often and other aquarists in Poland enjoy them.

Poland is an emerging fishkeeping country with some great breeders, planted tank and reef enthusiasts. What is the hobby like in your country and is it easy to get good fish/corals/equipment?

There aren’t any problems getting equipment in Poland, or, if I need to, I can have items sent from abroad. As for buying animals, the choice is more difficult, especially when it comes to health and condition. That’s why I transport many corals from Germany, and, most frequently, from individuals.

Have you had any problems along the way?

Yes, but they weren’t serious. I had to catch some pests that came with some new corals, but I reacted immediately. They never became a plague.

What would you change about your existing set-up?

Nothing, but I would like to have a bigger tank. I haven’t made any current plans for the future.

What do you think is key to the great success of your current aquarium?

There is no simple key. It depends on many factors, such as knowledge, patience, ability to draw the right conclusions from observation, routine maintenance, keeping stable water conditions and the appropriate equipment.

First and foremost you should be fond of reefkeeping. Your tank isn’t a beautiful piece of furniture, it contains life that you ought to take care of with all your heart.

What’s in the tank


  • 1 x Purple tang, Zebrasoma xanthurum.
  • 1 x Sailfin tang, Zebrasoma veliferum.
  • 1 x Chevron tang, Ctenochaetus hawaiiensis.
  • 1 x Tomini bristletooth tang, Ctenochaetus tominiensis.
  • 1 x Canary wrasse, Halichoeres chrysus.
  • 1 x Flame angel, Centropyge loricula.
  • 7 x Green chromis, Chromis viridis.
  • 1 x Orchid dottyback, Pseudochromis fridmani.
  • 11 x Lyretail anthias, Pseudanthias squamipinnis.
  • 2 x Common clownfish, Amphiprion ocellaris.


The fish are fed frozen food (such as Mysis, krill, Artemia, mussels), Cyclop-Eeze, Spirulina, and Nori twice a day. No more fish will be added to the tank.


About 50, all SPS except for Scolymia, Cycloseris tenuis, Ricordea florida and Zoanthus.

Fact File

Tank: 160 x 80 x 55cm/63 x 31 x 22” display tank with 704 l/155 gal gross volume. 110 x 50 x 52cm/43 x 20 x 20” sump.

Total system volume: 750 l/165 gal.

Length of time set up: In 2003, but glass and equipment upgraded since.

Circulation: Two Tunze Turbelle Stream 6105 and two Iwaki MD55 combine to circulate 32,000 lph. Additional Red Dragon 8000 lph circulates water from sump 56 times total turnover.

Lighting: ATI Power Module eight 80w T5 plus an additional one 80w T5 bulb are on for 12 hours a day, from 9am-9pm. Six bulbs are on for seven hours a day, from 10am to 5pm. Also a moonlight. Total lighting 720w. 1.02w of T5 per litre.

Protein skimmer: Korallen Zucht Revolution M, rated for between 1,500-4,000 l/330-880 gal system volumes.

Calcium supplementation: Liquid supplements added using Balling method, via a Grotech TEC III NG.

Water parameters: Alkalinity: 7-7.5; calcium: 420-430 mg; pH: 8-8.2; magnesium: 1,380-1,400 mg; temperature: 26°C/79°F; PO4 (phosphate): 0,02 mg; NO3 (nitrate): generally 0 mg; salinity: 35 ppt; density: 1.026 s.g. (25°C/77°F)

Water changes: 10% per week and an additional 20% per month on top.

Method of nutrient control: Ultra Low Nutrient System, using bacteria and zeolites in a Korallen Zucht magnetic Zeovit reactor.

Other equipment: A Teco chiller and a Profilux controller for temperature, redox, conductivity and pH.

This article was first published in the November 2009 issue of Practical Fishkeeping magazine. It may not be reproduced with written permission.