The Beginner’s Stocking Thread
By: Dan


You may or may not be aware that this site has a very active message board area. It covers all aspects of the hobby. Recently there was a very important thread started on the stocking of aquariums and this article will be a compilation of the ideas posted In the threads.

While the owners of “Badman’s tropical fish” agree with most of ideas posted here we make no formal endorsement of them. I will say that the posters of the boards are some of the most knowledgeable, friendly and helpful people I have ever had the pleasure of working with and would put a lot of confidence in their comments.

  • From Dan
    • The number and size of the fish you keep in your tank should be based on several factors. It should not be based solely on the chemistry of your water nor on the magic of the inch per gallon myth. It’s more than simply a matter of successfully keeping the ammonia and nitrites at zero or the fact that you may have “great filtration”. certainly these are important issues, but one of the most important factors is almost always overlooked. The number and size of fish that one maintains in a tank should be predicated on the “biology” and behavior of those fish. This means that the interaction of a mixed community tank and/or the behavior of a single species, is the single most important factor to consider. You want the fish you’re keeping to have the ability to exhibit “normal” and functional behavior. Normal behavior is important. Abnormal behavior results in stress. Stress leads to disease.

      Disease can lead to death. For example:


      1. If species (A) does not get along with species (B), then these fish don’t belong in the same tank no matter how few fish you have or how large the tank. “Getting along” is based on the visual and behavioral Q’s that each fish species is genetically programmed with. This is why African cichlids don’t belong in the same tank with Central American cichlids for example. Africans don’t “understand” Central American fish speak and this leads to behavioral problems and stress.
      2. If species (A) has specific food or water chemistry requirements which are completely different from species (B), then these fish don’t belong in the same tank no matter how large it is.
      3. If a spawning pair of species (A) is aggressive and defends a territory of 2 square feet, then you cannot expect to successfully keep more than this pair in a tank which is smaller than 2 square feet. Convict cichlids are an excellent example of this … this little fish aggressively defends territories of about two square feet give or take. If you have a tank which allows only that much room and no more, the convict will defend the entire tank to the detriment of any other fish (no matter how large it is) in that tank.


    • Fish need room to swim without having the rest of the tanks inhabitants “in their face” continuously. When crowded, fish exhibit stress syndromes that result in poor color, improper fin form, insufficient metabolic development, do not exhibit proper musculature, do not develop properly functioning organ systems and most importantly slowly lose their inherent resistance to disease. This results in a significantly shortened lifespan and along the way, lots of diseases for which the poorly conditioned fish is a good target..
    • Think about your local lake or river — the fish are free to inhabit whatever space suits them biologically. If it gets crowded by their standards, some will disperse and move to other areas where they again have the space they need to exhibit functional behavior.
    • It’s difficult to allow for that “space” in your tank — the fish have no escape within the confines of your tank so it’s up to you to insure that the fish have that space in the first place. If your tank “looks bare” .. it’s probably just right.


  • Jessica’s Comments:
    Fish keeping is a joy and a responsibility. Tossing some fish in a tank and seeing what you end up with is certainly one method, but not what I would think is the most responsible. I’m sure many of you here will agree with me.
    Important Factors to look at when Stocking a tank:
    . Tank Size
    . Tank Decoration
    . Tank Mates
    . Aggression/territory
    . Schooling/shoaling
    . Zones
    . Biotope and continents
    . Plants
    . Water Maintenance

    Tank Size

    is what most people look at when they stock. It is quite important, as it will dictate what the largest fish is you can have, thus, putting an initial limit on your fish. As I go on, you will find there are many other limits, just as important. If you were to visit your fishes’ homewaters, you would discover a wide variety of homes that support a unique collection of fish best suited for their environments. You also will notice that many places consist of deep water, and lots of it.

    A great number of fish available are actually wild-caught. Most of the ‘staples’ are bred in ponds, but if you pay attention to the ‘rarer’ fishes, that come through once or twice a year, you will find that many fish are coming from areas of massive water to your small tank. Thus, there are some fish that get pretty massive themselves.

    I like to have a general rule of not keeping a fish in the tank that the ADULT fish will not exceed 1/6 of the length of the tank, and 3/4 to 1/2 the depth of the tank. This means, that in a tank with a footprint of 36×12, you want to keep the largest fish being 6″ or less. Rules are made to be broken and there may be exceptions, but for anything less than a 55 Gallon, I’d keep this very closely. Please note, what I said, the ADULT size. While it is incredibly hard, even for me, to keep things in mind of the full-grown fish, you must consider that. The fish will grow, and if you cannot continually purchase more and larger tanks, you will find yourself being irresponsible.

    Some fish grow slowly, others don’t. The slower ones, like clown loaches, you can afford to upgrade tanks as you go, provided that you don’t wait too long. Some of the faster ones, like common plecos, will rapidly need a new tank, and you will find yourself spending alot of money to keep up with the upgrade demands. In those instances, it is better to not purchase those fish until you have an appropriate tank waiting for the fish.

    Tank Decorations.
    These actually should be planned around the chosen fish. This is actually important to stocking because a properly decorated tank will increase your fish’s comfort and lower stress. While stress is inevitable, there is no reason to cause undo stress because you felt like having only those bubble-making skeleton in your tank. Research your fish. Don’t keep fish that need sand in a tank with gravel. (Once you set those things up, their a pain to take down).
    If the fish need rocky caves to feel comfortable, a fully planted tank isn’t going to cut it. They WILL need their rocks and caves. For some fish, you won’t find the information just looking around.

    Sully offered an idea awhile back: offer the fish multiple options and see what they choose. You will find that cories are generally not cave-dwellers, but prefer a well planted tank to meander through. Botia species need tight-fitting caves and holes, and they don’t mind if its wood or rock, just its gotta feel like they’ve been stuffed in a sardine can. Schisturas need rocky caves, these can be a little more spacious, but still nothing outrageously large. Tetras and pencilfish like plants to be able to lurk in the foliage when their comfort level drops. Plus, its a safety net, they will be more secure swimming around the tank, if they know there’s somewhere safe to dart to. Shell-dwellers demand shells. And the list goes on.

    If your fish likes/needs caves, find out what kind. Chances are, they will not want anything where the hole is too much larger than their body height. Bumblebee gobies, for example will not use anything where more than 2 bumblebee heads will fit in the opening. If you think about it, it would be easier to defend a smaller opening than a large one. I’m sure there are exceptions, but every cave-dwelling fish that I’ve offered a choice, rejected the ‘ideal’ man-made roomy cave for something they barely fit in.
    So if you want a well-planted tank, or don’t want to mess with plants, or don’t want sand, this will/should affect what fish you choose to place in your tank. Also, don’t forget to offer enough caves to suit ALL your different fish who need them, in fact, have a couple extra.

    Territories and Aggression amongst tank-mates.
    These are not synonymous terms. Fish can need a certain amount of territory, but not be aggressive, but all aggressive fish need their territories. You can get around this, by keeping a solitary fish in your tank… or can you?

    Like people, fish have their bubbles. Each fish is different, but most follow the generalities of their species. Knowing these fish’s bubbles or having a general idea of them will help you out. Many times, places like badman’s forums can help you out with this (at least with the basic of fish and a few not so basic). They can tell you that a gourami’s bubble is larger than a 10gallon tank. Thus, placing 2 gouramis, dwarf or otherwise, will result in a dead fish.

    It is better to find this out ahead of time if you can. And pay attention to what you read. I didn’t pay attention to the numerous comments on the aggression level of botia robusta. I lost several fish to them before I discovered who was the culprit was. Other fish, when not given their territories will stress and likely harm themselves, and can even die. Bala sharks will be my example here.

    These fish have HUGE bubbles. If you do not offer the fish at least part of their bubble, they will spend too much time hitting the glass walls of the aquarium, or soaring for clearer waters over the tank’s edge.

    Some fish will have territories that overlap. An example would be an angelfish, school of tetras, school of cories, and a pleco. All these fish have requirements, but they are willing to share with a different kind of fish. The angel (provided the tetras and cories are large enough to not be considered food) will disregard them as a threat, and perhaps gain comfort from the smaller “stupid” fish moseying around the tank. The pleco could care less about the cories, after all, his thing is the driftwood, and chances are, he’s nocturnal, or will at least wait until you disappear. 😉

    And some fish do care about the overlap, or rather, they need a large enough home to tolerate an overlap of territories. These guys are the aggressive ones, and sometimes they are best kept singly. If they are to be kept with others, make sure you do your homework, as mistakes here will cost fish lives.Schooling and shoaling fish
    Sometimes, one fish truly is not enough. These are my favorite fish, and my down-falling.

    I will loosely define schooling as fish who stick pretty closely together most of the time. Schoaling is the fish who need some friends, but its more a social thing. Its a little easier to define by sorting fish into the groups. (You will also find that everyone has their own definitions of schooling and schoaling)

    I would consider tetras, cories, and barbs, rainbows as schooling, and many loaches, cories, and some cichlids are schoalers. Schooling fish MUST be kept in large groups. Minimum is 6, better is 10+, best is 24+.

    Schoalers need at least one or 2 friends of the same kind.
    I’m going to use my good friends, the clown loaches and cardinal tetras for examples. By my definition, Clown Loaches are schoalers. I have 9, which makes for a decent school of anything. However, these guys will split apart into groups. The only time I see them all in the same place is at dinner time. Cardinal tetras are schoolers. When relaxed, they will spread out throughout the tank, but every now and then, they have to do a head count, and they all amass and circle the tank, leaving out no one. They will lurk in the plants together, rarely splitting up. I only noticed splits when I had a group of 23 green neons and 11 cardinals in a 125 gallon tank. Even then, a group of merely 3 was unthinkable. When one fish split off from the pack and started exploring, the entire group started streaming after them.

    This will also bring us to another issue within this area. With shoalers, it is easier to get a larger variety of similar species. But when it comes down to schooling fish, I highly recommend minimizing the different kinds, unless you can find out if those tetras are accustomed to seeing each other in the wild.. a true biotope.
    While its desirable to have 2 each of tetras A through Z, it really isn’t fair to them. And it isn’t fair to you either. Some will school together, (more so those with similar body structures), but you will never see anything so impressive as a true school. There also is increased stress with the numerous kinds. You will find that keeping a single kind will allow for more fish than keeping mixed. For this reason, I do not advise more than one type of tetra in a tank less than 4 feet. Perhaps in a 3ft, you might get away with 2 kinds (smaller species).

    Shoalers… Don’t plan on being able to place as many in a tank as the schoolers. While you could have 24 small tetras in a 20L, you don’t want to stuff a ton of botias or schisturas, they might get a spine in their eye and decide to take out their tankmates. Not usually the case, but shoaling fish can be slightly territorial as well as requiring friends to spend the night with. I placed cories in both sections, because I’m still at a bit of a loss with these guys. I’ve only kept pigmy cories. Those guys are definitely schoolers, and anything less than 10 isn’t proper. The regular cories, I have not kept, but everyone seems to find a group of 3 enough, which means they don’t fit in my schooling definition. Personally, I’d want to keep them all in groups of 6.. but that’s just me.Zones

    It mostly was covered in the Territories Segment. But it wasn’t addressed as this. Some fish prefer rocks, others open water, some cling to the ground. Considering all these can allow you to stock a tank to its fullest.

    Continents and biotopes
    I’m still not sold on continents as being the second most important thing to consider when planning your tank, however, they are something which are worth considering. In my mind, if you are going continental, you might as well go biotope. However, I’ve found the best argument for this coming from Russ. So I shall quote:

    quote:Lets put this scenario into another perspective. A zoo. There are lions, tigers, buffalo, gorillas, deer, sheep, etc.,and could be hundreds of other animals from all over the world, housed in relatively close proximity.
    Would they all survive and thrive together in the same cage? Probably not. A zebra, lion, gorilla, antelope, and giraffe all come from the same continent. Will they thrive together in the same cage? Probably not.
    Each of those animals has it’s own ‘nitch’ and conditions that are most favorable to them. Some have larger nitches while others have very small ones. Just because a lion can survive at Brookfield Zoo, just outside the Chicago city limits in winter, doesn’t necessarily mean it’s thriving there. (Although the zoo folks do do a very good job of caring for the animals there). Would the lion be a little better off in a zoo with warmer climates all year round? Probably. But, the are exceptions to this also. Mountain lions here in the US live and thrive through winters. However, would a mountain lion and an African lion do well together in the same cage? They are both lions.

    I like considering the temperaments. Perhaps a deer and an antelope wouldn’t be a bad combo together. Obviously, when you mix continents, it is best do do so with docile fish that are of compatible temperaments. Yet, even going back to my thoughts of a deer and antelope.. For some reason that does not sound quite right, why is mixing fish different? Its a question I haven’t gotten an answer to.
    Yet, I’ve seen no undue stress on my bristlenose plecos when they share their home with African cichlids or Asian loaches. Heck they are breeding, and the female right now looks like she could hire on for Blimpies mascot. Most definitely consider this aspect. When you mix ANY fish, make sure to watch them carefully. Even from same continents, they may decided they don’t like each other much. Learn what ‘happy’ is. Learn what stressed is.

    pose many considerations. In short and sweet, they take away swimming room. Reduce space for the fish to swim in, but also give comfort. They can break up territories. Plants remove harmful nitrogen wastes and in general, are the best thing you can do. Some fish, plants reduce the number you can have, other, they will increase them. A heavily planted, well filtered tank negates most bioload issues. Some fish will not allow plants to remain planted. Others need a mainly rocky build, which removes the ability to use most root-bound plants. However, there are many alternatives. Floating plants and mosses do not need gravel or to be anywhere in the tank. You can spend as much time researching plants as well as fish. If you are planning on going planted, do yourself a little favor and find out what you want to do, and what you need to before you end up with your tank filled and with fish and deciding you need a new substrate.

    Water Maintenance
    . This is vital.

    Freshwater fish love freshwater. Bioload issues can be reduced by more frequent large water changes. However, keep in mind that this takes time and effort. I believe it is Russ who says to Don’t buy the largest tank you can afford, buy the largest tank you can afford to maintain. I think it can also be extended to, do not stock your tank beyond the maintenance levels you can keep.

    There are many cool fish out there, and believe it or not, there are ones which will fit your tank that you will find to be very desirable as well. Some may require, effort, planning and hunting, but even those small tanks can be stocked with fish that will continue to delight you.

  • Russ’s Further Comments:
    Meeting a fish’s primary requisites may enable some mixing. It may be 50/50 or less over the very long-term, but for many of the bread & butter-type fish, it can be done. A primary requisite for a certain fish may be temperature and diet, and some degree of territory. It may also include, but not limited too, being in groups. And of coarse, the biggie….water conditions. If you have fish that have the same primary requisites, then there will be less of a problem keeping them together.

    There are certain ‘comfort’ or temp requisite zones that fish have. Some are tighter than others. There are certain ‘comfort’ or temp requisite zones that fish have. Some are tighter than others. Outside of those temp zones, a fish may be able to survive with no great difficulty, but combine that with other stress factors and that can spell a slow demise for the poor critter.Guppies do much better in water with a slightly higher alkalinity and temps of approx. max of 76F. Can you think of another fish that has those same requisites, but do not encounter guppies in the wild? Perhaps platys? These are critters that do well in shoals, schools, and in tiny groupings, and feed all over the tank
    Aggressive fish do not necessarily mean that it is a fish that will eat any other in sight. Aggressiveness does not necessarily apply to carnivores. Although predation may be seen as the highest form of aggressiveness, a four inch African Mbuna defending it’s algae turf can be 10 times more aggressive than, lets say, a PiranhaQ: Many times we say your fish can adapt.. If you are keeping fish in higher alkalinity, would that change things? or would you suggest to only buy fish that meet your water type?
    Russ’ Answer fish can eventually adapt, but not as quickly as a lot of folks think they can. It takes a fish an average of 10 days to adapt to pH changes in one’s tank. For example, a new purchase being brought home. For expensive fish and ‘lovable’ fishes (which really all are), its best to have a quarantine tank for them to adapt. I know its not practical for many folks, but after all, this is a hobby:-)One must still keep in mind that 99% of environmental requisites for your fish are controlled by you. Kind of like the thing from The Outer Limits. You control the water. You control the diet. You control the stocking. Etc…
    OK, I’ve been thinking for awhile, and it would be nice to compile a stocking thread. This would be how to stock for new fishkeepers. I would appreciate it if, when you get the time, folks post good tanks. Debates can ensue, corrections, anything horribly out of whack will be edited. In essence, this is a chance to offer a learning resource for those who would rather research than post, and even for those who post. When offering tank stocking ideas, make sure the tank size and dimensions (not listed in the table) are clearly stated.


  • New Fishkeepers’ Resources
    Please read this link if you are planning a new tank set-up: Table of Basic Aquarium Sizes. If stocking a tank other than one of these, please post a list of dimensions.

    Volume Volume Dimensions Dimensions
    Gallons Liters Inches Centimeters
    5.5 21 16 x 8 x 10 41 x 20¼ x 25½
    10 38 20 x 10 x 12 51 x 25 x 30
    20 76 24 x 12 x 16 61 x 30½ x 40½
    20L 76 L 30 x 12 x 12 76 x 30 x 30
    29 110 30 x 12 x 18 76 x 30 x 46
    40 Br 152 Br 36 x 18 x 16 92½ x 46 x 41
    55 209 48 x 13 x 20 122 x 33 x 51
    75 285 48 x 18 x 20 122 x 46 x 51
    90 342 48 x 18 x 24 122 x 46 x 61
    125 475 72 x 18 x 20 182 x 46 x 51
  • Jessicas’ thoughts5.5 Gallon Tank
    1 betta
    2 African dwarf frogs (unclawed)5.5 Gallon Tank
    3 male guppies
    2 small shrimp (Amano, ghost, cherry, or related)29 Gallon Tank – Planted
    1 pair small/dwarf/docile cichlids – I’m thinking South American (SA) (max 3-4″)
    1 school of one kind of small tetra (10-12, max size 2″)
    1 bristlenose pleco or small pleco OR 1 small school cories (6, max 2″)translates into:
    1 pair rams
    10 cardinals
    1 albino bristlenose pleco

  • Cindys’ thoughtsI’ll add some of my favorite smaller tanks, since these are the ones people seem to need the most help with:10 gallon tank – a half dozen male and a half dozen female Endler’s livebearers and up to two dozen fry. Fry/juvies should be moved to a grow out tank as numbers or sizes increase.20 gallon long tank – one pair of kribs or jewel cichlids and their fry.55 gallon tank – 1 male and 4-5 female yellow labs or red zebra cichlids125 gallon tank – both groups mentioned in the 55 plus one 1:4 group of powder blue (P. socolofi) cichlids

  • Debbs’s thoughts10 gallon planted tank
    3 female bettas
    2 apple snails55 or 75 gallon planted tank
    4 Microgeophagus Ramirezi (German Ram; Blue Ram; Butterfly Cichlid; Gold Ram)
    3 Angel Fish or 3 Discus
    10-15 Cardinal Tetra’s
    School of cory catfish (6)

  • Kims’ thoughts37 gallon (same footprint as a 29 but taller.)
    I like my choices here because the whole tank is used and the species are peaceful together.3-Botia Striata on the bottom
    3-Gold Barbs, use the middle of the tank mainly, with trips up and down
    6-Blue danios, mainly hang out in the upper section but do venture down when they feel like it.
    Cherry shrimp
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