Danios settling in

Danios are in

It has been almost a week since the Danios were added, they have settled in well and are relatively bold, but do not seem to appreciate when someone walks quickly across the room (as is expected). They certainly seem to enjoy the piece of wood, spending much of their time swimming through the holes in the base and around the stems, but do come right to the front of the glass when they notice me looking at them. The females are receiving plenty of attention from the males and one is looking considerably more plump now, so they may spawn soon.

The fish found the flow of the filter to be disturbing, so I have attempted to slow it down by wrapping filter wool around the rough sponge and placing more still between the sponge and the bio media. It seems to have helped slightly, but not enough, so I am still thinking about how to slow it down further. The stand building project has come to a bit of a stand still as I am quite lazy, but this has given me an incentive to get it going again because the external filter has a 300 lph rating compared to the 700 lph that came with the aquarium.

The fish are feeding well on frozen Daphnia and Artemia, with a supplement of high-protein granules and generic flakes. The 10 fish eat only tiny amounts, so even the smallest tub of fish food will last for years at this rate. Given that most fish food goes off in a matter of 1-6 months, it makes sense to separate it into smaller containers, freezing or chilling the majority of it until it is needed.

There have not really been any major signs of algae, I am still cleaning off mild signs of diatoms from the glass every couple of weeks, but that is it. Most of the plants are doing well, and I plan to split up one or two of the Cryptocoryne parva bunches into individual plants over the next week.

Methods of acclimatisation

Since I had the tests out and I also had some spare test tubes, I decided to test the water which the fish were coming from:

  • KH: 6 ° (107 ppm)
  • GH: 16 (286 ppm)
  • ammonia: 0 ppm
  • nitrite: 0 ppm
  • nitrate: 20-80 ppm
  • pH: 8.0

As can be seen from the above results, the difference between that and the aquarium water is quite significant! If I was to move the fish straight over, they would probably get quite a shock from the difference in hardness, so I would need to acclimatise them first.

My preferred method of acclimatisation is often referred to as “drip acclimatisation”. The process is simple, although time consuming:

  1. I start by gently tipping the bag with the fish and LFS water into a bucket (8-10 litres for small fish, larger for larger fish), have something ready for covering the bucket as many fish are able to jump
  2. If the fish has been in transit for any significant period of time, or you have any other reason to suspect that there is ammonia in the water, add a product which temporarily converts ammonia into ammonium
  3. Add some décor and/or plants to make the fish feel more secure and relaxed
  4. Add a heater and airstone if needed, for example, if the air temperature is cooler than the aquarium water or if the fish have been in transit for a long time
  5. Next, set up an airline with a knot tied in it so that the flow can be controlled, to drip 4-10 drops of aquarium water into the LFS water per second for a 9 litre bucket (depending on how sensitive the fish are and the difference in water parameters: the smaller the difference, the faster the flow), for larger buckets, a faster flow should be used, for example, 10-20 drops per second for a 20 litre bucket so it takes approximately the same amount of time to fill
  6. Once the bucket is full, which usually takes 3-6 hours, remove the airline
  7. Transfer the fish from the bucket, into the display aquarium using a net, trying to minimise water transfer by not even dipping the net in the aquarium
  8. Disconnect all equipment that was used
  9. Throw away the water in the bucket (I water house plants with it)
  10. Disinfect all equipment used and throw away plants which were used during acclimatisation
  11. Top up the aquarium with dechlorinated water

The more common method involves floating the bag in the aquarium for a short period of time and occasionally adding large volumes of water to it: this does not particularly help the fish become accustomed to the new water and can be as harmful as not acclimatising at all. From what I have seen, this is one of the most common reasons, after ammonia poisoning, for deaths in new fish.

Importance of acclimatisation

Fish are osmoregulators, which means that they regulate the water levels inside their bodies by means of a process called osmoregulation to keep the salt concentrations inside their body constant, regardless of the fluctuations of salt outside their bodies. The process differs in freshwater fish and marine fish because of the environment, I will write about the freshwater process as that is what concerns this aquarium.

Some species of fish, such as some Poecilia spp., are able to tolerate a very wide range of salt concentrations in water, all the way from fresh to marine water: these fish are called euryhaline. But most (common freshwater aquarium) fish are not able to tolerate changes in salinity: they are referred to as stenohaline.

Water hardness is made up of metal ions and carbonates, both of which form salts, so harder water contains more salts than soft water. This means that it takes more work for fish to maintain body salt concentrations in softer water and less in harder water: keeping hard water fish in soft water can affect their health as they would constantly be putting more effort than is usual into maintaining their bodily functions.

Most fish have a blood salt concentration of 9 ppt, while fresh water has a salt concentration of under 0.5 ppt, so freshwater fish tend to try to maintain salt concentrations in their blood at higher levels than the water is at, which is achieved by ion intake through food and gills and by excretion of excess water by means of a dilute urine.

Most fish are not able to instantly adapt between different water hardnesses, which is why moving a fish from one water type to another quickly can result in death or serious injury. To avoid problems, it is important to acclimatise the fish to the new water parameters over a long period of time and with only small changes in the water parameters. In theory, if the start and end water hardness, pH and temperature are same or very similar, acclimatisation can be skipped.

Long term exposure to water types the fish are not suitable for cause increased susceptibility to diseases, because of the extra work that hard water fish have to do in soft water and because many diseases do not do as well in soft water, so soft water fish are not always as able to resist them.

Deciding on fish numbers

Most aquarium fish can be classed into one of three living preferences:

Schooling and shoaling:
These fish, depending on the species, live in groups that range form a few hundred to a few million individuals. Home aquariums are most often not able to hold groups that large, but the bigger the group the better it is. I usually recommend that one should aim to keep 10 – 15+ individuals per schooling species as there is no excuse to not do so if stocking a new aquarium. Unfortunately, some people find out that they have only a few individuals from a schooling species after the aquarium is fully stocked, in which case it is best to try and increase the numbers to at least 6 individuals per species or to find them a new home. In some way, fish are aware of individuals up to a point, at which the individuals become “many”. I think that 6 individuals is this point for many species. One of the most important functions of schooling is to protect the individual fish from predators, either by letting the weaker fish in the group be picked off first (as easier prey) or appearing as one larger fish. The main difference between schooling and shoaling fish is that shoaling fish will normally only swim in a tight formation when threatened, usually going about their own business (for example, Trigonostigma heteromorpha). On the other hand, schooling fish (such as Paracheirodon innesi) will spend most of their time swimming close together, even to the point of facing the same way. The group includes fish like tetras, rasboras, danios, barbs, many loaches and rainbows. One unusual member of this group is Neolamprologus brichardi, a shoaling cichlid.
Small groups:
There are a few different variations of small groups which can be found. These include small groups of social fish, which do not have much social structure (such as livebearers) or which have a specific social structure (for example, cichlids); closely knit family groups; pairs of breeding male and female couples; harem groups of one male and a number of females (often seen in many Apistogramma species), or quite rarely, one female with some males. As with schooling fish, small groups provide security for individuals. For some mildly aggressive species, such as Pterophyllum scalare, it may even be possible to keep them peacefully only individually, in proven breeding pairs or in small groups of more than 6 individuals because the dominant fish can then spread the aggression over multiple individuals, instead concentrate it on a single one.
Some of these fish are too aggressive to keep with any others of their own kind, and in some cases, even with other fish which would occupy the same area inside the aquarium, while others simply do not interact with one another on a regular basis. This group includes some loaches, cichlids and gouramis.

It is quite important to try and keep the fish in appropriately sized groups as some may otherwise display odd or aggressive behaviour. The easiest way to find out appropriate stocking numbers is to research the conditions in which the species is found in the wild.

Some basic research showed me that Danio margaritatus and Yunnanilus sp. ‘rosy’ is a peaceful, mid-water schooling fish, which automatically means that I should be considering 10 individuals per species. This is a good number to start with, and there is always the option of adding more later.

Pseudosphromenus dayi, on the other hand, is a solitary fish which breeds in pairs. Males may occasionally be persistent, so I decided that it is better to have 1 male and 2 females, to give the females a bit of a break in case of uninvited attention.

So for my first “final stocking”, I will be aiming at the following:

  • 10 × D. margaritatus
  • 3 (1m 2f) × P. dayi
  • 10 × Y. sp. ‘rosy’

It is very common for final stock to evolve with time, which is why I am referring to this as my first one. As for how I decided on the total number of fish? That is rather difficult to explain as there are no set rules, nor have I seen any good guidelines. I chose the number based on my experience and I always base my decisions on adult size. The stocking numbers are also affected by the amount of plants in the aquarium as they will use up ammonium. For an aquarium which is 60 × 30 × 30 cm in size, I would normally expect to stock between 6 individuals of the larger species I list and 25 individuals of the smaller species. I would also stock conservatively if I pick female livebearers because they will drop fry and it is best to reduce chances of overstocking.

The best advice I can offer on stocking is to not stock more than one feels comfortable with, even if others say that the aquarium will take more fish, and if one is being advised to stock less than one plans to, to try the lower stock first.

Pseudosphromenus dayi

Since I am now unable to collect the Danio margaritatus, I will be moving the Pseudosphromenus dayi to this aquarium instead. This anabantoid comes from Kerala, the most south-western Indian state where air temperatures range from 15 to 36 °C, which I assume corresponds to water temperature of 16 to 34 °C. The fish have been found in fresh and brackish water, usually in lentic conditions, and may be very common in Chalakkudy River, Muvattupuzha River and Periyar River. There are some claims that this species can also be found in south-east Asia, but this is very likely to be a mistake caused by a mislabelled P. cupanus holotype.

As with other Osphronemidae, P. dayi possesses a labyrinth organ as well as gills, which allows it to breath air instead of extracting oxygen from the water as most other fish do. The labyrinth organ is located in the gills, at the first gill arch. I have read of research done into the breathing of Betta splendens, another labyrinth fish, where results showed that without access to air, the fish suffocated, so it is safe to assume that fish which have a labyrinth organ do require access to air at all times.

Apparently, the fish can grow up to 75 mm, although one of my females is currently at 30 – 35 mm and the male is around 35 mm at, by my estimate, at least one year of age. Fish are normally measured nose to base of tail for consistency, as tails can vary in length between individuals; with the tails included, the same female is around 45 mm and the males is close to 50 – 55 mm.

Mature males of the species have more orange throats, considerably elongated and pointier dorsal and caudal fins, and slightly elongated anal fin compared to females. Juveniles are almost impossible to sex unless the males’ fins have already started growing longer and I have found that the orange throat is usually more noticeable when the fish are ready to breed.

These gouramis are not shy, but do require plenty of plants as they spend most of their time under leaves. I currently have three of these fish in a 420 litre aquarium, where each one has taken up residence in a specific group of plants. One female has chosen a large Anubias barteri (spending most of her time under one of the broad leaves or swimming thought the roots), the other female has taken up residence in some plants which have floated to the surface, while the male lives in a patch of Cryptocoryne wendtii ‘brown’ (I often see him wrapped around one of the leaves). Flow does not seem to matter much to them as the females are both in areas where there is almost none, while the male spends much of his time about 15 cm away from a circulation pump, which is pointing directly at him. They are not strong swimmers, so I would say that a densely planted aquarium or one with low-flow areas is compulsory. The aquarium is 60 cm tall, but all three fish spend their most of their time either within 15-20 cm of the bottom or inside floating plant clumps, with the exception of feeding times, when they happily come out into the open.

As with many other gouramis, P. dayi is a surface feeder and their natural diet includes insect larvae. In an aquarium environment, they readily take all prepared and live foods of appropriate size. They are a slow feeder which takes its time to come out for the food, so it is important to make sure that they receive their portion of the food, especially if they are kept with fish which are known to be greedy for food.

P. dayi are compatible with most peaceful, community species, with the usual exception of other labyrinth fish and those which are big enough to eat them. Because they are a slow species with a flowing tail, they will make prime subjects for abuse by fin-nipping species, so it is best to avoid those.

The species breeds in pairs, with the male building a bubble nest inside a cave or under some leaves. The female lays approximately 200 to 300 eggs, which sink to the bottom and are collected by both parents before being spat into the nest. The eggs are guarded by the male and will usually hatch within 24 – 36 hours. After a few days, the fry use up their yolks and become free swimming.

P. dayi are currently classed as vulnerable by the IUCN, so it is worth looking for aquarium bred specimens over wild caught ones. Deforestation and agricultural activities, man-made pollution, mining and destructive fishing are the main threats to their habitat.

After more than a few hours of searching, I finally located the journal that the species was originally described in on Google books, but I am unable to find somewhere that I can download it from. For reference, the species was originally described as Polyacanthus cupanus dayi by W. Köhler in 1908. The paper, Untersuchungen über das Schaumnest und den Schaumnestbau der Osphromeniden, was published in Blätter für Aquarien- und Terrarien-Kunde, Stuttgart, volume 19 (pages 392-396). If anyone has a copy of it, please let me know as I am interested in reading it.

Picking species…

So, I was a little impatient and started looking for plant and fish stock… and of course, I grabbed the plants when I saw them (also made arrangements for more species in a few weeks) which means I should spill my ideas about now. I will be using mainly scientific names because many fish have various common names associated with them and some are common between different species.

Various fish species prefer different areas of the aquarium, so unless one is careful about filling all the levels, soma parts of the aquarium may end up being completely empty, while the fish concentrate in others. There are three main levels to consider:

These are fish which either spend much of their time at the surface because they are surface feeders or breath through labyrinth organs. Most common of these are gouramis, Bettas, hatchetfish and some killifish. These fish often have superior mouths.
Mid-water schooling fish are most common, they are usually found in groups of a few hundred to many thousands, in the wild, which is why they do best if kept in groups of 6 or more, but even better in groups of 10 – 20 or more. Some examples of schooling fish are barbs, danios, rasboras and tetras. Other mid-water fish also include many livebearers and cichlids. These fish usually have anterior mouths.
Bottom and surfaces:
These fish are often grouped together, but make up two quite distinct groups: fish which live towards the bottom of the aquarium and those which live on surfaces and the bottom itself. The first group include earth eating cichlids, some loaches and some Corydoras, while the latter consists mainly of plecos, shrimp, the remaining loaches and Corydoras. The large majority of these have inferior mouths, although some do have anterior ones.

Because the aquarium is only 60 by 30 cm, it restricts me to only the smallest species, as I want my fish to have enough space to turn around and interact with their environment. So, I am restricted to about 30 mm for active schooling fish and 50-75 mm for fish which have low levels of activity. I am going to go for the standard configuration: one group of schooling fish, one group of “bottom feeders” and a couple of centrepiece fish.

First, I need to decide on which fish I wish to focus. As I have not kept loaches in the last five years, they are one of the species I want to look at. Also, living in Germany, has given me access to many unusual species, such as Boraras, so this is starting to look like an Asian themed aquarium. Asian leads me to thinking about gouramis and Bettas, my LFS currently had some Betta channoides, B. strohi, Parosphromenus deissneri, Pseudosphromenus cupanus and P. dayi. So I do a search of all these species, first on Fishbase then read the first ten search results for each, as the internet is not exactly renowned for the accuracy of all information. Average results show me that all species are suitable. I already happen to have a pair of Pseudosphromenus dayi, so they’re going to fill my “centre piece” and “surface feeders” slots.

Now, that leaves me with need for a “bottom feeder” and a “mid-water schooling” species. I start searching through Planet Catfish for small catfish and find Erethistes jerdoni and Erethistes maesotensis, from some experience and conflicting search results, I know that Erethistes and Hara are used interchangeably. I haven’t decided if I really want to go for catfish and loaches, so I’ll just keep these in mind for now.

So now I start looking at loaches, for which, unfortunately, there is no good species resource like Planet Catfish, and come across Yunnanilus cruciatus and an unidentified Y. sp. ‘rosy’ (also known as “Tuberoschistura arakanensis”). After some more searching and enquiries, I decide that Y. cruciatus is on the too large side, and Y. sp. ‘rosy’ is about right. Both of these small loaches are schooling fish, and tend to swim mid-water.

Last, but not least, I looked at the schooling fish.. I was originally planning to go for a Boraras species, but I discovered that Danio margaritatus are from the same location as Y. sp. ‘rosy’. I generally prefer to aim for biotope or at least the same continent or water type, and I have been wanting to keep D. margaritatus for many years now. When this species was first discovered, their habitat was almost destroyed by the greed of fishkeepers everywhere, and the wholesalers falling over themselves trying to collect the species. It has now been a few years, but I will still not buy these fish if they were wild caught, so I am now searching for captive bred specimens. I would also like to mention another interesting species of the same size is Danio erythromicron, it is also very unusual, but an excellent find for a small aquarium.

I will continue with numbers of each species, stocking order and plants in the near future…