Fishes for the nano reef aquarium

Fish | 13th February 2013 | Article by Albert Thiel | View comments (12)

General rules on stocking your nano aquarium

The first, and perhaps the most important rule, is not to overstock your nano aquarium, and overstocking applies not just to how many fish you house in your tank, but to the total number of life forms you have in the tank, so it includes corals, crustaceans, invertebrates, echinoderms, cleanup crew members, and anything else you have in the tank.

If your aquarium is small, e.g. 40 gallons or less, it is not be a good idea to place a number of schooling fish in it, as when you do you many not be able to add any other fish to that nano aquarium.

In smaller tanks, e.g. smaller than 20 gallons, it is not a good idea to add one or more Clownfish to the tank, even small ones, as they will grow and when they do, they will want to “own” the entire tank and will chase any other fish in the tank around. All Clownfish are territorial and like to consider your entire nano aquarium as theirs and will therefore harass any other fishes that are in your nano aquarium. If they do not do so when they are young and small, believe me as they grow into more adult ones their genetic build-in traits will take over, and territoriality will begin.

When this happens the fish or fishes that are being chased may become so stressed that they get diseased, or in a last ditch effort to avoid the aggression they will jump out of the tank if they can, or because of the being chased they will not be able to feed enough and will eventually start showing signs of starvation (sunken belly syndrome being the most common). Even if you have a cover, and if there is a small opening anywhere in that cover, I can assure you that they will more than likely find it (e.g. where electrical wires come through). Once they get out, or get stuck in the opening they found, you have in essence lost the fish. Many fish too are jumpers and often for no specific reason, so make sure you are aware whether the ones you get are or are not (the fish section lists a number of them as you will read).

If they cannot get out of the tank and keep being chased around, they will become exhausted, or will hurt themselves by brushing against your LR (live rock) and the injury may get infected; or due to the exhaustion they may get become infected with marine ick (Crytocaryon irritans), or the injury may get infected and a bacterial disease will be the certain result. Bacterial infections on fish can be treated as we shall see later, however corals with bacterial infections are a far greater issue.

Even if the fishes you are considering are not schooling ones but are conspecifics and housed in a small tank (e.g. males and females of the same species, or several males, or even at times several females) aggression will set in as they may consider each other to be competitors for space and food. And this does not just apply to fish but to certain crustaceans as well (certain types of shrimp for instance).

Keep in mind also that what may be fine in a larger tank may not work out the same way in a nano aquarium due to the limited amount of space and the lesser amount of water in the latter type.

Also make sure that you know what fishes you are considering feed on so you don’t end up, for instance, placing a fish in the tank that consumes your shrimp or your snails. This applies not just to fish but to anything you want to add. Hermit crabs can be a real problem in that respect and I will deal with those later.

Mixing it up

Do not mix shy type fish, e.g. a number of smaller Gobies, together with fish that are known to be more aggressive or dominant, as the result will more than likely be that the smaller and shy ones will be outcompeted for food and starve, or will go into hiding never to be seen again.

Mind you they may still be alive and feed on what they can grab in areas where other fish cannot aggress them, but what good is it to own a fish that you never see. And if at times they do come out they will get chased around and you may lose them for the reasons explained above. Either that or as I mentioned they will just remain in hiding.

Stonogobiops nematodes

Stonogobiops nematodes

A good example of such a fish would be a Yellow Rose Goby – YRG (Stonogobiops nematodes), which in the presence of more aggressive fish will stay in hiding most of the time, if not all of the time, and may only come out during the early night shortly after the lights are out, and dash out and back into its hiding place after maybe having caught a small piece of food. I have one in my 20 Gallon nano aquarium and about the only time I see the fish is when I spot feed in the exact area where he has his burrow, which is underneath a large rock, and which is well protected from other fish in the tank so that when I spot feed they do not swim to that area and try to hijack the food.

Note that fish with similar feeding habits may also cause a problem for each other, although that is not as common as aggression for the other reasons described. It is a possibility though and one you may want to keep in mind when selecting fish for your nano aquarium.

Feeding habits

When choosing fishes and corals, or other life forms, know what their required feeding habits are and make sure you cater to them, as if you do not, or do not know what they are, you will more than likely lose that fish, or coral, or crustacean or other life form.

Synchiropus splendidus

Synchiropus splendidus

A good example would be adding a Mandarin Fish (Synchiropus splendidus) to your tank, a fish that requires special feeding of copepods (pods), on a practically continuous basis, or it will not survive. In addition, depending on what else is in the tank, even if the pods are there, it may be outcompeted for food by other fish.

Be aware too of other behaviors of the fishes you are interested in, especially whether they are so-called “jumpers” or not, and if they are whether you are prepared to put a tightly fitting cover over your tank to prevent them from jumping out.

Purchasing your fish

Whenever you buy fish at a local fish store I suggest that you ask the staff to show you that the fish “is” eating, and find out what it is being fed so you can continue to feed the same food. If the fish is not eating my suggestion is that you do not buy it.

This is especially important for fish that are known to be picky eaters for which you want to make sure that they are not on a starvation diet, as if they are there is no sense for you to buy them, as the fish will not survive for long in your tank. Don’t try to be the savior as getting fish that are on a starvation diet to eat is just about impossible. Don’t waste your money on such livestock. There are more than likely plenty of other fish around at that store that you can buy and that will eat and not give you any issues afterwards once you place them in your aquarium.

When buying fish also look at the overall appearance of the fish, meaning does it look healthy, does it have a sunken in belly (in which case do not buy it), is it breathing normally etc. Buy only healthy looking specimens that you can witness eating.

Keep in mind also that some fish will dig burrows in the sandy substrate, some digging deeper ones than others, meaning that if you are thinking about buying most Gobies, that you do need a place for them to do so.

Gobiodon citrinus

Gobiodon citrinus

There are exceptions to the Goby rule and your LFS should be able to tell whether a substrate is needed for a particular fish, whether a Goby or not. For instance, the Citron Goby is definitely an exception to this rule (Gobiodon citrinus), and is a great fish for the nano aquarium and a most playful one and a pleasure to watch for its behavior at times.

Other fish like to hide in crevices or little caves in the live rock in your tank from time to time, so your LR must have those types of areas for them or they will not do well for you. Or you can arrange your aqua-scaping in such a manner that such areas are available to those fishes.

Although not so commonly considered an issue, it does happen: fish with approximately the same coloration, markings, and body shape may consider each other as threats and may, as a result become aggressive towards each other. This is not a frequent occurrence, especially if your tank is 30 gallons or larger, but it can be an issue in a small tank that is, for instance, around 15 gallons or smaller.

Firefish and Dottybacks should not be kept together in smaller nano aquariums as invariably the Firefish will “jump” if it can, or it will end up being harassed so much that it will not make it for very long.

Avoid any fish that is at some point likely to nibble or pick on corals, not to consume or eat them, but out of curiosity, as the constant picking at the coral can lead to a wound that can get infected, or can lead to the coral deciding not to open up fully, or not at all. If that happens and the coral does not open it is not getting light and if it is a photosynthetic one, it will lose it zooxantellae and will die off in a short period of time, as it will not derive any foodstuff from its symbiotic algae.

And as a general recommendation, even though a lot of store owners will suggest that you add Damsels to your tank, any kind of Damsels, my recommendation is to stay away from them as they are all aggressive, even if not immediately, but they will be at some point.

It is not really possible to give you a list of fish that you can put in your tank as what you can add depends on what is in there already, or what you may want to add at a later time.

Fish that don’t belong in any nano reef

Below are two fish you do not want in your tank, as it will eat or gobble down anything that is smaller than itself and even fish that are of its own size.

Pterois volitans

Lionfish (Pterois volitans) – The tank Fish Vacuum. © Nick J Webb (flickr)

Dendrochirus brachypterus

Dwarf Lionfish (Dendrochirus brachypterus)

Both are gorgeous fish and very popular but if you wish to keep one it should be housed in a species tank and not in a general nano aquarium one. Not only do they have a voracious appetite but they need live food and are not easy to acclimate to anything else, although it can be done (e.g. to morsels of shrimp or clam or other meaty foods).

What’s in my tank you ask?

So after all the “do not’s” and “watch out for’s you may be wondering what do I keep in my own tank. And rightfully so! So let me briefly describe the system I run and what I maintain in the nano aquarium.

I currently have a 20-gallon High nano aquarium set up that is running with an HOB filter, and HOB skimmer, and an Oxydator™ from Söchting, Model D, which is rated for tanks up to 100 liters (approx. 26.5 Gals). At this time I do not have a sump or a refugium installed. Lighting consists out of 2 CFT (Compact fluorescent tubes) rated at 100 watt equivalent, and with a 6500 K rating. True wattage is 2 times 23 watt.

I use GAC, GFO and Poly-Filters from Poly-Bio Marine™ and filter floss where the water first enters the HOB Aqueon™ filter that acts as the mechanical filtration and that I change every day (I do not have to use a lot so the bag of filter floss lasts me weeks and weeks). I will also use Aluminum oxide as a phosphate and silicate remover, and typically what I do is alternate their use. I never use both that the same time though, as that would create issues as the PO4 and SiO2 levels would drop too fast in the tank and that would have negative reactions on the corals.

The tank contains the following fish:

  • A Bi-Color Blenny (Ecsenius bicolor)
  • A Yellow Rose Goby (Stonogobiops nematodes)
  • A Banggai Cardinal (Pterapogon kauderni)
  • A Citron Goby (Gobiodon citrinus)
  • A Lantern Basslet (Serranus baldwini)

I also have several Cerith and dwarf Cerith snails, Nerite snails in the tank, two Nassarius spp. ones, no Hermit crabs, and a black Stomatella varia (the black variety shown on this page) which feeds on algae and is mostly nocturnal.

A number of unidentified small snails came in as hitchhikers (HH’s) and, based on what I can see they are all omnivores and feed on detritus and whatever small algae growth they can find on the live rock, and leftover uneaten foods.

Pterapogon kauderni

Pterapogon kauderni

Of course as in just about any nano aquarium that has live rock in it (and which one does not?) I have an assortment of worms that are crawling around on the rock and in the sand, but as is the norm, I rarely see them during the day. Most of them come out at night of course and forage for detritus and uneaten food, and are not harming anything as they are mostly garden variety “bristleworms”.

I plan to add at least one more fish to my tank, but given what I already have in it, the fish needs to be relatively small, but not too small, peaceful but able to hold its place in the tank and not allow itself to be bullied should one of the ones in the nano aquarium already try to do so.

I really had my eyes on what is called a Coral Croucher (Caracanthus maculatus) because of its habit to sit on, and in crevices in live rock, but it is a carnivore and once I put one in my tank I cannot add any

Caracanthus maculatus

Caracanthus maculatus © Tristan Lougher

SPS corals such as Acropora, or any branched ones. Indeed it likes to hide in there and could damage the coral’s tissue, and if it decides to spawn, it lays it eggs on the underside of them, which will eventually lead to tissue necrosis, and the eventual demise of that coral. So although it is a very interesting fish, I do not feel that it is a good choice for a nano aquarium, even if you do not have SPS corals as it may decide that your shrimp or other small crustaceans look appetizing and gobble them down.

Elacatinus puncticulatus

Elacatinus puncticulatus

So instead, and looking at what I have in the tank already, I think I may decide on a Red Head Goby (Elacatinus puncticulatus). Its behavior is somewhat similar to the Yellow Rose Goby (YRG), in as much as it will dig a burrow for itself, and dash in and out of it to capture food, or to inspect what is going on. It also digs a lot and keeps sand in its mouth to move it out of the way or place it where it wants it.

Of course, and even though one can add more than one sand digging Goby In one’s nano aquarium, depending on the size of course, the Yasha is best placed in the nano aquarium before any other burrow making ones are added so it can find its spot and become comfortable in the tank.

Stonogobiops yasha

Stonogobiops yasha

Stonogobiops dracula © Randal JE (fishbase.org)

Stonogobiops dracula © Randal JE (fishbase.org)

Yasha Gobies prefer meaty foods such as Mysis shrimp or brine shrimp, and will eat other foods as well but not as their mainstay. Whenever up get any fish, and as pointed out before, always know what they feed on and before buying any at an LFS make sure you see the fish eat. If you get them online, make sure you have a guarantee that they will feed, and know ‘what’ they have been fed by the seller.

Yet another favorite Goby of mine and of many nano aquariumers is the Dracula Goby (Stonogobiops dracula), a stunning looking fish, and also one that digs a burrow and that like many other Gobies creates a relationship with goby shrimp, both of which will occupy the same burrow. The Dracula is not as commonly available as other Shrimp Gobies and tends to be on the pricier side. It is a gorgeous looking fish!

Having listed a number of Gobies a note is in order that you cannot place too many of them in a nano aquarium. Unless your tank is rather wide and larger than 30 gallons, my recommendation is to keep their number to two, and two of the smaller ones as there are also a number of larger Gobies.

Other options that you have include:

  • Watchman Goby, Cryptocentrus cinctus
  • Sleeper Goby, Valenciennea wardi
  • Banded Goby, Amblygobius phalaena
  • Bar Goby, Ptereleotris zebra
  • Catalina Goby, Lythrypnus dalli
  • Clown Goby (Black), Gobiodon acicularis (these come in several colors) Note: At times Clown Gobies will nip on SPS corals so they may not be the best choice is you have those types of corals in your nano aquarium
  • Cave Goby, Fusigobius inframaculatus
  • Engineer Goby, Pholidichthys leucotaenia
  • Purple Firefish, Nemateleotris decora
  • Helfrichi Goby, Nemateleotris helfrichi
Nemateleotris decora

Nemateleotris decora

And many more, so if you decide on one or more Gobies for your nano aquarium, do some additional research so you understand their care and requirements, and know about their compatibility with other fishes in your nano aquarium. Gobies are generally very pleasant fish to up in your nano aquarium as they often demonstrate interesting behaviors that are fun to watch.

My Citron Goby, for instance, is a real trooper and behaves in the most peculiar behaviors at times, like hugging the glass for extended periods of time, or lying down inside one of my large Cabbage Leather corals, or perching inside a Sarcophyton coral, and more.

The gobies of the family ‘Gobiidae’ are one of the largest families of fishes, with over 2,000 species in more than 200 genera. Most are small, typically less than 4” in length. They also include some of the smallest fishes in the world, e.g. Trimmatom nanus and Pandaka pygmaea are only 3/8“long when fully grown. Large gobies, such as some species of Gobioides or Periophthalmodon, can reach up to 1 foot. in length, but that is unusual. Another fish you may want to consider, but that grows fairly large, is the Lawnmower Blenny (Salarias fasciatus), which is an algae eater (algaevore) and usually a good tank

Salarias fasciatus

Salarias fasciatus

companion for most other fish you may be keeping in your nano aquarium, but can grow up to 4 to 5 inches, although in smaller nano aquariums they remain quite manageable. Often, when kept in smaller aquariums, many fish will not reach their full size and may in some cases remain quite a bit smaller but this does not apply to all fishes. They have a great personality and you can keep several in your tank as long as you introduce them all at the same time. If that is done there may some aggression although it will usually subside after a while.

The issue with placing many algae eating fish in the same nano aquarium is that it is likely that there will not be enough food for all of them to eat and you will therefore need to supplement their diet with, for instance, seaweed sheets that are commonly available in the trade and may come in flakes, or pellets, and even in sheets that you can attach inside the aquarium with a special holder. It is said that many Blennies like to dig in the sand and that may well be true but they do not need the same type of tank arrangement as Gobies (with whom they are often confused).

Blennies tend to have large eyes, cirri (lashes over their eyes) and rather long bodies. Some can grow fairly large around the reefs but in Aquariums they tend not to grow larger than 3 to 3.5 inches in most cases. They make excellent nano aquarium fishes, but as always make sure that when you select a particular kind that you familiarize yourself with their habits, their needed care and food requirements.

Photos: All photos in this post are © Wikipedia unless otherwise noted.

About the author:

Albert has published a number of reefkeeping related books including possibly the first book on 'nano reefing' entitled, Small Reef Aquarium Basics - for smaller tanks and for beginner hobbyists. Other titles include the best selling The Marine Fish and Invert Reef Aquarium, Advanced Reefkeeping I, Advanced Reefkeeping II (e-book) and The New Marine Fish and Invert Reef Aquarium (e-book). In addition to his books, his work was regularly published in magazines including his own monthly, The Marine Reef Newsletter. In addition to his writing Albert has spoken at numerous aquarium conferences and meetings across the world. Albert is currently finishing up his latest book, Nano Reef Aquarium. Click here to pre-order your copy of this exciting new book.

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12 Responses on Fishes for the nano reef aquarium

  1. Owlbassboy says:

    I have a red head goby in my nano and he doesn't have a burrow, he darts constantly through the crevices in the rock and rests in the rock not the sand.

    Have to disagree with the generalisation about the damsels as I know loads of people that have no issue with damsels. Allens are a peaceful damsel, sure there may be the occasional thug in there but isn't that true of any fish we own?

    But aside from that disagreement lol it's a brilliant article and hopefully an awful lot of reefers new and old will learn from it ;)

  2. Albert Thiel says:

    There are always going to be exceptions to just about any rule that applies to Nano and other reef aquariums so I am not going to disagree with you but IMO Damsels do not make good Nano-Reef fishes, just as Clownfish do not either in the long run especially. Both grow and can be intimidating to other more peaceful fish that one has in a Nano, so as I pointed out, the mix and the compatibility also have to be taken into account. Typically as time goes by Hobbyists add more fish and more corals and so keeping the peace in the tank becomes an important aspect of success. Whereas a Damsel may be fine if there are only 2 or 3 fish in a small tank, once more fish get added IMO it is best to avoid any fish that "may" cause a problem. Just my take on the matter. Also on the Red Head Goby: most of them do make burrows if they can and clean it out and take sand in their mouths and sift it, but again exceptions do exist and yours may be one of them. How deep is the sand bed that you have and do you have other sand digging Gobies in your tank maybe? Thanks for the kind words and this is only Part I in a series of articles on Fishes for the Nano Reef, so as we go along you will find that the "keeping the peace" does indeed become a factor that you can agree with and that it pays to avoid any fish that "may" cause problems at some point in time, even if at first it does not.

    I appreciate your comments.

  3. Owlbassboy says:

    There is a randalls goby under one rock that actually has very little sand and there is another bigger rock with about 2-3" of sand around it (the mp10 is pretty powerful) I will be closing this tank down soon to focus on long term pico reefing. My current 12l has only been running about 8 months but I will be disappointed if I don't hit 5 years.
    I reef very much with the opinion that less fish is usually better, well at least more smaller fish are better in smaller tanks than a few bigger ones. My 12l even has 2 trimma gobies in it I do think they may be the same sex as they don't go near each other one lives up top on one side of the scape while the other lives down low on the other side.

    I suppose the damsel point really does depend on the tanks stocking plan, I do get where you are coming from about hitting that point where things can go wrong when either fish grow or more are added. Too many of us are guilty of not forward planning when stocking our tanks

  4. Albert Thiel says:

    Thanks for the additional info on your tank and sorry to read you are closing that tank down to focus on the Pico, a fascinating type of aquarium indeed. And yes well maintained Picos can certainly last for years and years but of course need even more care in the selection of what life forms are placed in it. A section of my new book deals with Picos and I have some pictures in it showing Brandon429's 1 gallon Pico. Amazing tank. And yes on the Nanos, longer term thinking is a very good recommendation indeed, unless one starts removing fish and/or corals to replace them with others, which can of course be done, but is IMO not what most Hobbyists will do. They may keep adding and adding and cause compatibility issues on one hand, but also water quality problem ones, as the filtration that originally was what was needed may not be able to deal with an ever growing bioload. I have to end as I have to be on a Radio Show where I am talking for an hour or more in Nutrition for fish and corals (this one is part II as I had did the first part about a week ago). Thanks for your comments and all the best of Pico Reefing I can wish you.

  5. [...] Fishes for the nano reef aquarium, Albert Theil, Nano Reef Blog [...]

  6. [...] you ever picked out a great fish for your nano aquarium–only to find out that it simply refuses to eat anything you offer? No matter what tasty [...]

  7. Mike says:

    I`ve had great success with Yellow Clown Gobies. They will host corals and get no bigger than 1.5 inches in length. I`ve never had another fish chase them, although my pair will sometimes chase each other.

    • Albert Thiel says:

      Mike: indeed, they are great fish for a Nano, and are best kept with some Branching SPS corals so they can emulate their normal and natural behavior in your tank. And as you know, if you have a pair they will actually breed even in smaller tanks. They deposit their egg mass on the underside of an SPS branch and protect them as best as they can but unfortunately the eggs never make it to fry … and the little tissue damage the egg mass leaves on the polyp is minor and will heal in a relative short period of time.I love the Green ones too, and of course I have a Citron Goby in a 20G tank as you may be aware of. Thanks for the comments
      Albert

  8. Helen says:

    Thanks for the post! Nano reef aquariums are great!

    • Albert Thiel says:

      Thanks Helen, and yes I agree, Nanos are great indeed, but as you know they require more careful maintenance as due to the smaller volume of water they contain, monitoring conditions and keeping the tank well balanced and up to par is a definite must so things do not get out of hand, and so the Hobbyist remains “in charge” of the tank and not the opposite. Thanks for the comment.
      Albert

  9. Buhajer2 says:

    I have 6 gallon tank. Am planing to keep one fish( Six-line wrass) sherimp. And same corale. How many of coral i can keep and snails

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