Nathan's tank is a mixed reef that I have visited several times over the past five years. Initially I was worried that you guys might be sick of seeing another video of his tank, but I double checked and the last one I published was 3 years ago! Let’s catch up and see how things are looking!

This tank is a 72” long x 30” wide x 22” tall aquarium made by Aquarium and Glass Exhibits which is a little over 200 gallons. What is obvious right away is that it is a mature reef tank and loaded with giant colonies of SPS. What might not be so obvious is the fact that Nathan’s aquarium looked this full for the past five years despite having sold off enough coral to fill several additional aquariums.

That is part of the reason for my visit actually. In addition to shooting some footage of this tank to share on this channel, I am also here to pick out some aquacultured corals for propagation at Tidal Gardens. People always ask where I get my corals from. I do work with some importers for corals that are not easily propagated, but whenever possible I get corals from local hobbyists.

There is a big difference between acquiring corals fresh from the ocean versus getting them from an established reef aquarium. Corals grown long term in captivity are much more hardy than wild caught specimens and are much less likely to have pest issues. If I had a choice, I would buy absolutely everything aquacultured and once the systems in my new building are up and running, you can bet that I’ll be paying another visit.

Frag Tank or Show Tank?

What I really like about Nathan is he is like a rare art collector. Anyone with sufficient funds can put together a collection of art with established names and high values but the really good ones collect pieces that the rest of the community is sleeping on today but will fully appreciate tomorrow. Nathan has a great eye in that regard and his taste in coral is ahead of the curve. There have been plenty of occasions where he’s shown me a new acquisition that I didn’t think much of and within 12 months is selling for a fortune.

Nathan warned me that his aquarium these days looks like more of a frag system than a display tank, but it still looks pretty good! He’s not wrong though. He is collecting a ton of different corals all at once and you can see many of them in various stages of propagation laying around on the substrate.

Fish Selection

Some of the more uncommon fish in the aquarium are this Tamarin wrasse that not only looks sweet but looks like it does a number on potential pests. I can tell just by its behavior that it would do a great job because it is constantly hunting in and around the corals. If I could find a bunch of them I would love to include them into the wrasse army.

He also has this absolutely massive blue star leopard wrasse. It looks like it is 8” and just the scales on this fish look oversized.

He still has this Orange Spotted File fish which spends most of the day nibbling on Acropora polyps. I personally would never recommend this fish for a reef aquarium, but it goes to show you if you have enough coral density, the explosive growth of coral outpace the destructive influence of these fish.

In this tank there is also a couple of rare fairy wrasses. I would love to get my hands on something like this. I think it is a Goldon Rhomboid Fairy Wrasse and it is definitely something you don’t see every day.

Last fish I’ll point out are these square block anthias which are full adult size and look super relaxed. When I see fish that are just frantic in a tank it stresses me out so for my viewing I like fish like this.

Reef System Design

Now that you have a little bit of background on this tank let’s cover the system in detail and see if we can learn something that can translate to success in our own tanks.

The first thing to note is that the system volume is significantly more than the 200 gallon display tank. There is a smaller frag tank situated to the left of the display that is plumbed in as well as a large sump in the stand. The overall system might be in the neighborhood of 300 gallons. Overall water volume does wonders for chemical and thermal stability.

Live Rock and Aquascape

Another benefit to the size of this display is the ability to add seriously large quantities of live rock. Live rock does a lot of positive things biologically for a reef aquarium such as providing a substrate for beneficial bacteria as well as small nooks and crannies for amphipods and copepods to spawn. I personally like to put in a lot of rock into a reef tank, but there is an art to aquascaping it in such a way that it doesn’t turn into a solid wall.

What is interesting about this particular aquascape is that it is practically unrecognizable from how it was first constructed. The coral growth is so extensive that it is hard to see any open patches of liverock. What is even crazier is that the shape of the rock today is completely different than it was a few years ago. SPS corals, especially Acropora are known as reef building corals because as they grow and die build up the reef structure. That process is happening in this tank where an original piece of live rock is covered by 5 layers of stony coral growth and is now double the original thickness.

Calcium and Alkalinity Dosing

Nathan sustains all this stony coral growth with a very tight dosing regimen of two part solution. For those that are relatively new to keeping stony corals, it is important to provide them a constant source of calcium, alkalinity, and magnesium. There are different ways to accomplish this, and dosing a two part solution of calcium additives and alkalinity buffers is the chosen route for this tank. At different times each day a dosing pump system inject a few ml of solution to balance out what the tank inhabitants soaked up out of the water.

People sometimes ask how much they should dose in a particular sized tank, say a 100 gallons, but the dosing requirements are all about bioload of stony corals rather than the water volume of the aquarium. A sparsely populated giant tank won’t really require very much in the way of supplementation where a densely packed tank will quickly deplete calcium and alkalinity. Also, as corals grow the demand for these major compounds skyrockets so it is necessary to check these parameters occasionally to make sure that they are set to properly reflect the demand of the reef.

One such device that helps with this is this Alkatronic. This is a separate unit than the dosing pumps that execute their own program each day. The Alkatronic tests the alkalinity of the aquarium and if it is low, will itself dose a small amount of buffering solution to correct it. It is not intended to be a primary source of alkalinity supplementation but something that helps monitor the levels and provide minor tweaks when necessary. Heavy automation can be worrisome to some hobbyists that have had a bad experience with a device reading an incorrect value and going haywire. It can happen to just about any type of automated system from an auto-top off, to a dosing pump, to a pH controller… pretty much anything CAN go wrong especially if the devices are not properly maintained.

The Alkatronic does have some safety features that are interesting. For example, if it performs its daily test and the value is far off the historical values it tested recently, it will test again before it does any type of correction. In essence it is looking for consistent test results before performing any remedy. Also, it is possible to limit the extent of its correction so that in the event that it tested incorrectly x number of consecutive tests, it will NOT unload the entire alkalinity container into the tank.

As with any automatic device nothing is 100% but I am curious to try one out for no other reason than the more frequent automated testing. I would like to see daily graphs of these measurements and if they are amazingly consistent then I might trust the device to do some adjustments with the alkalinity supply.

Magnesium Addition

Earlier I mentioned that stony corals need calcium, alkalinity, AND magnesium. Sometimes you see systems dose all three components separately. Nathan chose not to have a separate dosing system for magnesium, just one for calcium and one for alkalinity. To maintain magnesium, he integrated it with his continuous water change system. In a separate room, there is a 55-gallon water container with pre-mixed salt water that he then adds a magnesium supplement to to raise the levels.

Continuous Water Change System

The water change system is made up of two dosing pumps, one to remove water from the tank and down the drain and a second to bring in new salt water in an equal proportion. For this tank, it gets a 7 gallon water change each day over the course of several hours.


Water from both the display tank and the frag tank comes down to this sump. This is another sump that came in multiple pieces for ease of initial install, but the challenge is always getting the two units to connect. The connection here was done using a uniseal that you push a PVC pipe through. Usually you see uniseals implemented when you want to push a pipe through a cylinder shaped wall such as a reactor or a skimmer but here it was done through a flat side of the sump. Nathan had a heck of a time forcing it through and he basically said if there was a leak he would just cry. It is not a lot of fun to push PVC through two uniseals like that. I can only imagine how long that took. An alternative would be to use a bulk head with gaskets on each side, but depending on the quality of the bulkhead might be more prone to leaks.

Refugium Section

The right side of the sump is a refugium. In short refugiums are a section of a tank or sump that excludes predators and herbivores thus allowing microfauna and decorative macro algae to grow. The benefits they provide include nutrient processing, passive feeding of the aquarium as the plankton makes its way back into the display tank, and also having a space that the hobbyist can temporarily house a fish or some coral that needed to be separated away from the rest of the tank.

The downside is, because there is no predation, unwanted nuisances can proliferate unchecked in a refugium such as brown flatworms or Aiptasia anemones that would otherwise be handled by species specific predators in the tank. If you want to know more about refugiums you can check out our video on the topic.

Protein Skimmer

Situated on the left side of the sump is a filter sock chamber that leads to the large protein skimmer. I personally am unfamiliar with this brand of protein skimmer but it is quiet and seems to be doing a great job in Nathan’s tank. Since the sump is located under the stand maintenance is something that has to be considered so most of the large model skimmers are designed to be short and fat to allow for the most contact area with the bubble column but still be short enough that the head can be taken off and cleaned without hitting the bottom of the tank. Obviously for contact time and area a super tall 8’ skimmer would be better, but for space constraints many of the in-sump models have under the stand installation in mind. We’ve made a video all about protein skimmers so if you are looking for more information on those, I’ll link that video as well.

One wrinkle to this skimmer is the air intake. Some reef aquariums struggle with low pH especially in the winter as the house tends to be sealed up and the CO2 levels build up. Higher CO2 levels in the air lead to lower pH as it forms carbonic acid when mixed with water. To combat this, some hobbyists run the air intake of their skimmer through the wall or window to get outside air drawn in rather than the stuffy air inside the house. This can help to some degree, but it is less effective than you might think. A lot of seemingly unrelated factors affect the performance of this hack such as the length of airline. Makes little sense. What Nathan did was install a CO2 scrubber on the air intake of the skimmer. This scrubber uses a soda lime media to bind up incoming CO2 and thus raising the pH in the tank.

By raising the pH to a more desirable level closer to 8.3 in the tank, it affects the biology of the aquarium and actually encourages uptake of calcium and alkalinity for faster growth. When Nathan installed this CO2 scrubber he immediately noticed a drop in alkalinity through his Alkatronic and actually had to up his daily dose of 2-part to compensate.

Removal of Bio Pellets and GFO

The last thing I will mention about the filtration in this system is what is missing from the last time I saw this tank. Nathan removed both a bio pellet reactor and a GFO reactor. A few years ago, he was dabbling with ultra low nutrient methodologies and was not happy with the results. Since removing them he noticed much better growth and extension in his corals, particularly LPS, mushrooms, and zoanthids that would sometimes just melt suddenly. I think that hobbyists sometimes underestimate how aggressively carbon dosing and especially GFO do their job and overdosing on those things can cause catastrophic problems. Even with hobbyists as conscientious as Nathan it can be a little too much and he has moved on from those methods altogether. Right now his nitrates sit around 15 ppm and phosphate around .15 ppm.

Water Flow

As for water flow, it is all provided by a small return pump and mainly gyre powerheads. I’m seeing more and more people go with these and I can fully understand their popularity. They are low profile and create a nice flow for very little electricity. Compared to my tanks at the greenhouse, he runs a ton more water flow so sometimes when I buy a colony of Euyphyllia or something from his tank, it swells to 4x the size once it gets to my tank because of the lower flow. Flow is great, but some corals really tighten up when they are blowing around constantly. It is the low flow that encourages corals to really extend.


Last bit of equipment to cover is the lighting. In the main display is the oldest of the old school LED’s, the AI Sol Blues. Yes, these lights have been running now for 8 years. It goes to show that you don’t need to overthink lighting. Most lighting fixtures these days will grow and color up corals just fine.

The light over the frag tank is an Orphek Atlantik which I like and don’t like. On the one hand I love the way it colors up the corals. The corals themselves developed amazing coloration under this fixture that uses a number of different colored LED’s compared to the old school Sol Blues which only have 3. The thing I don’t like about the Orphek is that is is really weird to film under or take pictures under. It has a very strange violet cast to is so the images come out goofy. Still, most people aren’t photography geeks and this light does a great job at it’s main function which is to grow and color up coral.

New Tank?

So what is the next step for this setup? As I mentioned before, this tank changes over the years but it is always packed like this. It has been full for a very long time and it might be taken down in favor of a larger tank. Nathan is thinking of expanding to a much larger show tank and I’m trying to talk him into building an aquarium utility room next door and have all the mechanicals there. I’m like that devil on his shoulder telling him to spend more money. Seriously though, this tank looks great, and I am excited to see what the next system will look like given more room to grow.

That’s all from this visit. Hope you guys enjoyed the look into Nathan’s setup. Until next time, happy reefing.

Than Thein

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