By Bob Goemans
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Dr Gs Marine Aquaculture 

Bob Goemans corresponds with Cheryl and Derric

Cheryl and Derric writes...

Hello Bob,

I have been looking for some answers for about a month now with no results. I was just told that you would be the guy to talk to. My wife and I have set up a 125 gallon marine tank. We are hoping to make a reef but have so far been unsuccessful. I guess I will start with what we have for a system. The tank is 72" x 24" x 18"tall. It has a hole drilled in the back that goes to the homemade 35 gallon wet/dry. Also in the sump is an airstone protein skimmer. The skimmer is about 18" tall and 8 to 10" in diameter. The water is returned by a 950 GPH pump. Inside the tank are two 804's and one 304 powerheads that circulate water. The two 804's have the filter cartridge on the bottom of each.

Inhabitants; 90 pounds of live rock, 10 pounds of live sand, 2 to 3 inches of aragonite. For creatures we have: 1 Coral Beauty, 1 Yellow Eye Tang, 1 Sixline Wrasse, 3 Green Chromis, 3 cleaner shrimp, 1 Arrow Crab, 1 Emerald green crab, 2 brittle stars, 20 blue leg hermit crabs and several red legged hermit crabs. For lighting we have 440 watts of Coralife VHO.

Now for the frustrating part. I have attempted over 30 Turbos (all from the same source) and all have died within 3 to 4 days of being in there. We are also down a star polyp, a green mushroom, and a tongue coral. All of these we were told would be fine in our tank. After about 2 months of set up we lost a carpet anemone within 5 days of being put in. The tank is currently almost 4 months old. We have seen no evidence of any algae growing, coralline or green. All the water came from our newly purchased R. O. unit and we are using Kent Marine Salt.


* pH - 8.2

* Salinity - 1.021

* Calcium - 425ppm

* Nitrate - As close to zero as possible

* Nitrite - Same as above

We are also adding Iodine, Strontium, and Magnesium. We added the magnesium because we could not get our calcium to raise in the beginning and the fish store told us it was probably due to a lack of Magnesium. We also have used powered calcium additives and a "Clarifier" solution.

So far we have been told anything from "I have no idea" to "It's just not that mature enough of a tank yet" but as I search on the Internet and find people that add corals from 1 to 2 months I don't know what to believe. Any suggestion or ideas you would have would be greatly appreciated.


Cheryl and Derric.

Bob replies...

Dear Cheryl & Derric,

Thanks for your letter and honestly, I see many areas that need attention. And, very possibly you have contacted the right person, as I've been in this hobby for well over 50 years. And because I've just returned from a business trip and my email is overflowing, I'm a little tardy in answering your letter. Better late than never, as I do care about my fellow hobbyists.

After reading your letter I'm not sure whether to start with what's right or needs correction! But we need to begin somewhere, so lets take each paragraph and comment as needed.

In the first paragraph you mention your equipment, which includes a wet/dry in the sump along with an airstone powered protein skimmer and the powerheads for water movement in the aquarium. If it were my aquarium, the wet/dry would go, and so would the air powered protein skimmer. Both would be replaced with a single quality brand venturi powered skimmer. I say this because the wet/dry is better suited for a fish-only system where its end product of nitrate is not of major concern. In a reef system, the goal is to maintain a very low nitrate level and any device producing that and dumping it into the bulk water is not the way to handle that compound. The best way in my opinion, is to have nitrate produced in the upper half inch of your sandbed and via diffusion, have it acted upon by bacteria in the lower portion of the bed. Of course, nitrate can also be produced on the outer surface areas of live rock and be oxidized in its interior deeper areas. And it seems like your sandbed and rock are handling the situation, but keep in mind your bioload is still quite low. Again, to have nitrate dumped into the bulk water in "reef systems" is a questionable practice! I should also say that some hobbyists use the wet/dry to help get their reef systems up and running. Not a problem, however, it's the long-term effect that needs to be addressed. For those that do so, I recommend removing the trickle media in equal parts over a period of three months, then dispensing with the device 'if' the system is equipped with a quality skimmer. And as for skimmers, air powered skimmers, in my opinion, are dinosaurs! They are no where near as efficient as modern venturi skimmers or those that use other means of aerating the incoming water supply. There are five brands that I highly recommend. (For those reading this letter, if interested, please contact me.) And keep in mind a quality skimmer not only helps to remove much of the matter that will eventually breakdown into nitrate, it also greatly oxygenates the bulk water. Two extremely important benefits for closed systems.

As for the water circulation powerheads, I would remove the bottom filter cartridges as they are probably not needed and they probably also reduce flow. Could very well be that additional filtration is not needed, nor would serve any useful purpose in your system. Besides, it's just one more item needing maintenance.

In the second paragraph you mention aragonite sand, but don't mention grain size. Hopefully its not extremely fine, as I would recommend a bed depth of about two inches using a sand grain size of about 2 - 4 mm. The thoughts behind that and other chemical and biological processes are lengthy, and if interested in knowing more about them, I suggest reading my newest booklet, which fully explains them. It and my other booklets and where to get them are explained on my website. But in a nutshell so to speak, the finer the sand the less diffusion of oxygen. The less diffusion, the greater the anaerobic area, therefore nitrate will not be converted into nitrogen gas, as the bacteria living in this area can only reduce it to ammonium, no further! And ammonium is a primary algae nutrient, even much better than nitrate. So hands-on experience over many years with many, many different types of sandbeds and aquarium systems has shown that if the choice is a bed directly on the aquarium bottom, a shallow bed of courser sand is the way to go. Otherwise, I would highly recommend the plenum method.

As for the amount of live rock for your size system, it's about what I would normally recommend, yet your selection of live stock is not what I would recommend for a new system. The Coral Beauty is something I would only recommend being added to a well-established system where there is an ongoing and adequate supply of live crustaceans, e.g., copepods. These fish usually waste away in most systems because they fail to get an adequate food supply and the worst place for them is in a new system. And, as for hermit crabs, they should never be added unless there is a need for them. In a new system, most will starve to death, only adding to system nutrient load. I usually recommend, depending upon system condition, not adding them until the system is about six months old. However, at least you didn't add too many. And, as for the emerald crab, if there isn't enough algae, it will also starve to death. They are good consumers of algae, but, without enough to eat, they quickly perish. As for the arrow crab, generally safe, however, not completely trustworthy, especially if you have cleaner shrimp, who can't protect themselves especially when they molt. I generally don't recommend having both species in the same tank.

As for lighting, the wattage appears sufficient, however, you do not mention the spectrum/Kelvin range. Hopefully they are in the 6500 to 10K range and that you have a sunrise/sunset photoperiod, and that light duration is somewhat in the range of 7 to 10 hours. I would recommend the 10K range.

Now for the 'frustrating' paragraph. I rarely if ever recommend Turbo snails! They are large consumers of microalgae and if not provided with an almost endless supply they quickly die. And when they die, they create a stinking mess that can easily pollute the system. They are also sensitive to handling, heat, and low salinity (which you have). They may be okay in systems that are experiencing a major algae bloom, but for most aquariums, the Astraea snails are far better. And unless you have an algae problem, about 15 would suffice in your system. As for the coral deaths, your salinity is far too low. Bring it up slowly to 1.025 - 26. If you want only a fish-only tank, than 1.021 is ok to maintain, but not for a reef system. As for slowly, that would be no more than .002 - .003 per day. If you do it too rapidly, your fishes' will experience osmotic shock. As for the anemone, they are difficult to maintain for most aquarists, and I generally don't recommend trying to keep one unless the goal of the system requires one. Also, that anemone death was probably helped along by the low salinity and too shallower depth of sand. Also, depending upon your tap water quality, you may want to consider DI equipment as part of your RO system. There's an article on my website concerning RO/DI equipment that you may find informative. The Kent Marine Salt is an excellent product. Except for your salinity, the water parameters mentioned are good, however, one extremely important water parameter and crucial to the formation of coralline algae is not mentioned - and that is alkalinity. Which should be maintained in the 3.5 - 4.0 meq/l range. And a quality calcium reactor would help resolve that part of the water quality equation and do away with liquid and powder additives.

In the next paragraph you note the additives being used. The need for iodine is questionable, and there's a lot to it that doesn't meet the eye of the average hobbyist. The same is true for strontium and magnesium. Magnesium level 'must' be related to salinity, and strontium if over dosed is hazardous, as is iodine. And that can easily happen if your not testing these parameters. In your case, I suggest not adding them.

I also have to question why a 'clarifier' of any type would be used! The use of these type products must have much forethought and not be used without a thorough understanding of what they consist of and how and what impacts there may be. Hopefully that was not a suggestion by your local fish store! And if your local fish store recommended adding magnesium without testing, I suggest finding another store or at least questioning the owner about this obvious misinformation. And if some of your animal purchases were also recommended by your local store and they knew your aquarium history, I would be quite upset with their level of customer care, or should I say "lack" of customer care. Could very well be you may want to find a good shop, and even if their prices are somewhat higher, give them your business.

Hope this has been helpful.



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