Guidelines for Rainbowfish Maintenance and Reproduction

I am writing this article based upon my observations over the past four years. Hopefully I can clear up some of the questions I am frequently asked by my "experience research." These comments are purely my own and if they differ from yours then I encourage you to write an article as well to further enlarge the collection of printed material on our observations for future collectors of these beautiful fish.

WATER CONDITIONS

I want to go over this first as this is the subject of most of the questions asked.

Water quality is of utmost importance for healthy rainbows. Water changes of at least 15% per week are required but I prefer 50%. Think about it...that is their "air". You wouldn't want to breathe dirty air all week would you?

Water hardness is a life or death matter as well. Too hard of water causes premature death due to the extreme stress it can cause. Some fish affected by too hard of water are: M. praecox, M. duboulayi, M. trifasciata (Goyder River, Wonga Creek, Wenlock River), P. gertrudae, R. ornatus (Kin-Kin and Seary Creeks), M.s. splendida (Kuranda), I. werneri and M. nigrans are the most sensitive that come to mind. I am using anything over 450 ppm for my basis for comparison. Of course any rainbow would be best kept well under this hardness.

Some rainbows which seem to have a tolerance to harder water include most New Guinea species: M. parkinsoni, C. campsi, C. bleheri,M. boesemani, M. lacustris, G. incisus, M. herbertaxelrodi,C. axelrodi, M. irianjaya, G. ramuensis, M. s. rubrostriata and C. fasciata. As for the Australian species: M. trifasciata (Running and Skull Creeks), M. s. tatei, M. s. inornata and M. fluviatilis seem the most desirable. All others not named fall into the medium hardness category and should be kept between 80-200 ppm (4 - 12 GH) for best success.

Rapid pH changes over a short period of time should be avoided when possible. Dramatic changes can cause death within a matter of hours. All rainbows should be acclimated slowly to different pH ranges. A pH of 8.7 and 5.8 should not be exceeded with a pH between 6.5 and 7.5 being ideal in the majority of cases.

I presently only use addition of salt in the water as a non-drug cure for fungus. Some of the mangrove fishes, mainly the Pseudomugil species, require some added salt in the water. Presently I do not keep any of these species so I will leave that to your experience.

I am a big supporter of tannic acid additions to the aquarium. In the waterways where a lot of the rainbows are collected tannin levels are high - especially where a lot of the M. duboulayi and R. ornatus exist. It also does miracles in enhancing the fishes' colors. I also use Tetra's blackwater extract in my fry tanks for the added vitamins. I have seen an improvement in growth in the fry tanks where the extract is present.

Calcium is a very important component in water chemistry as it provides the "building blocks" for good bone structure development. In soft water conditions proper growth will not be attained when feeding calcium deficient foods. Therefore calcium must be added. I do this by simply adding some oyster shell grit. This is available at most livestock feed stores. Usually one teaspoon per 10 gallons is sufficient. Due to its slow dissolving rate this usually will not affect the pH significantly.

BREEDING

This is the subject of a lot of frustration for many people - including myself. The biggest complaint I get is that "I can't get them to lay eggs. I've tried everything!" Some fish, no mater what you do, will not lay eggs. One of the least known factors in hobby fishkeeping is water chemistry. If you are not getting eggs, chances are it's not your fault. Just because Chris in Canada can spawn certain fish and Troy in Kansas can't does not mean Troy is not as good at it. Both Chris and Troy are capable but the water chemistry in these regions are different. There are a lot of different compounds in water and the compounds may vary from region to region. The only way to overcome this problem is to create the water needed to induce spawning. Adjusting water chemistry is expensive and time consuming. Unless you know exactly what you need to change the only method that works well is trial and error. I suggest that you keep fish that spawn well in your water and let someone else spawn the fish that do well in theirs.

Another problem you may have is that sources of city water change and therefore the water chemistry will also vary. In Colorado the water is usually drawn from reservoir stocks where it has had time to gain compounds from the reservoir substrate. In the spring and summer we get most of our water from snow run-off. Where I live in western Colorado the hardness of the Colorado river can change as mush as 100 ppm from spring to winter. The raising of fry is also affected by water chemistry but I'll get to that shortly.

The best way I know to encourage spawning is a combination of two things: food and water. Good diet is important for good healthy fry. The quality of the nutrients in the yolk sack is a direct reflection of the diet the adults are receiving. This will affect the health of the fry when it is developing in the egg and for the first few days after it hatches. A poor diet for the adults will hinder fertility and development of the eggs and definitely result in weak fry. A diet high in protein and calcium is required for good success. I use frozen bloodworms and freeze-dried plankton and obtain good results.

The water for your breeders should be as clean as possible to reduce stress and to induce spawning. Frequent water changes are done to achieve this. Large water changes usually will be followed by increased spawning activity.

Ambiance is important for good spawning success as well. The goal here is to create surroundings where your breeders will be as comfortable as possible. I do this with a dimly lit tank with dark substrate and with three sides of the tank painted black or dark blue. No plants are present but I do use multiple mops in different places in the tank. This allows the fish to choose an appropriate spawning site and once chosen they will usually return to that same site. Yarn colors are combined (different shades of green) as sometimes different colors are preferred.

FRY RAISING

In the sections before this some tips and methods are discussed and close attention should be paid to those. First I want to talk about tank setup. This is the simplest part. I use nothing but a bare 10 gallon (35 liter) tank with a Tetra billi sponge filter and a heater. That's it! Only when I am ready to hatch eggs do I fill the tank totally with new clean unused water with a teaspoon of shell grit. The hardness of water I use is 100 ppm and the pH is 7.0. I add 1/2 teaspoon blackwater extract to those tanks of known soft, acid water preferring fishes such as M. duboulayi, R. ornatus and M. nigrans but I doubt seriously that the addition of this to any tank is a bad thing. The addition of ramshorn snails after the fry hatch is a good way to process uneaten food in the tank.

In tanks which super small fry are being raised a solution of nalidixic acid, nitromersol and acriflavine is added at 1 week of age to inhibit fungal and bacterial attack. Basically I take a quart jar and add 1/2 tsp. nalidixic acid, 10 drops acriflavine and a few drops of nitromersol. Shake well and use 1 tsp. of this solution in 10 gallons of water. As you can see this is a weak solution but it does have some benefits.

The water temperature is kept at a constant 82° F (28° C) until the fry are at least 3/4 of an inch (2 cm). Then it is slowly lowered to 76° F (25° C) for the remainder of their stay in the tank. I use 10 gallon tanks because I do not like to transfer the fry as they grow. In my experience they are sensitive when small and the less you disturb them the better.

Another thing that should be avoided is handling the eggs. The best way I have found is to leave them on the mops and let them hatch normally. Tray hatching works but the bacteria present on our skin can and will harm the egg sometimes causing the egg to fungus even though it is fertile. When you are ordering eggs in the U.S. you should request mops and mops only unless the shipping time will exceed 4 days. (I have had eggs on mops in bags for 5 days and have been highly successful though.)

As for foods for fry - I use Artificial Plankton Rotifers (APR) almost exclusively with good results. Bio-Genesis is another product which works fairly well but it is nearly 10 times more expensive than APR in small quantities. Two pounds (about 900 gm) can be purchased for $200 US and 2 pounds of APR can be purchased for around $20 US - but this is more than you can use in 10 lifetimes.

Fry are fed APR for about 2 weeks or until able to eat baby brine shrimp At this time a combination of the two foods for about 1 week will ensure the slower growers can be fed as well. Small feedings of ground flake food should be given at one half inch (1.25 cm) of length so that they can get used to their adult diet.

In closing I must apologize for the length of this article. (being too short that is!) There is a lot more information that should go along with this but after all, I am not writing a book. Should you have questions about this article or questions related to it please feel free to contact me.

Good fishkeeping.

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