Why the serious fishkeeper needs a grow-out tank.


If you are an average fishkeeper, then I would suppose you have 2 to 3 aquariums at home. If you have more, then you are more than an average fishkeeper, you are a fanatic. If you only have one tank, then maybe you are in the hobby because you amazed after seeing a home aquarium somewhere, and may leave the hobby once frustrations set in. If you are an average fishkeeper, it is certain that you will not be able to control your urge to buy another fish… soon! Let’s face it: once you are hooked on fishkeeping, you will want to buy fish that catch your fancy.

Tanks Galore

Soon, your 2 or 3 tanks will grow to a number that will annoy those who live with you or make them think there is something psychologically wrong with you! You will only have limited space for tanks at home and at some point, you will have to stop. So you might as well be smart and selective with the tanks you set up. Fishkeepers may have one or a few main tanks where their best fish are kept and which are their favorites. These are well equipped and maintained; you might say it’s their crowning glory in fishkeeping. Then they should have support tanks, which are generally smaller in size and serve a specific purpose. One of these is the hospital tank for nursing sick or injured fish. Another is the quarantine tank, where newly purchased fish are kept for 2 weeks, just to ensure they are disease-free before you put it in one of the main tanks. For those who keep predatory fish and feed live fish to them, a feeder fish tank is also necessary; it is a very wise practice to provide a tank where you keep your feeder fish alive and healthy. Lastly, a grow-out tank is a valuable tank to have if you are seriously into fishkeeping. While the different support tanks are all important, in this column, let’s highlight the value of grow-out tanks.

As I wrote this column, two friends purchased Goliath African Tigerfish (Hydrocynus goliath) but made the mistake of putting their new fish in with their existing collection. The bigger fish in the tank made a meal out of the newcomers. While the Goliath African Tigerfish is a certified monster fish, these are oftentimes for sale as puny 4-inch fish—easily a nice meal for the big boys. This unfortunate incident could have been averted if they had grow-out tanks.

What is a Grow-Out Tank?

My definition of a grow-out tank is an aquarium specifically set up for newly purchased fish that are too small to be introduced to the main tanks. My premise here is based on the perspective of the fish hobbyist and not the fish breeder, whose definition of a grow-out tank is a spacious tank to grow fry to marketable size. There is no strict rule on the size of the grow-out tank; it’s not really a black and white thing. But there are important factors you should consider. Certainly it cannot be too small for the fish you wish to grow out.

If you purchased a tiny 2-inch Red Tail Catfish (Phractocephalus hemioliopterus) and bought yourself a 2.5-gallon tank, who are you kidding? The Red Tail Catfish will outgrow your 2.5-gallon tank in two weeks! Small tanks will not promote quick growth; they can stunt fish growth. It is a very well known fact that if you wish for your fish to grow fast, the tank should be big. The larger your grow-out tank, the better it is for you. As mentioned previously, size does matter and the bigger your tank, the faster you may expect your fish to grow. So the key is to get the biggest tank you can. My only apprehension about getting the biggest is that it shouldn’t be bigger than your main tank. If my main tank is my pride and joy, I would like it to be the biggest tank at home; the grow-out tank is a support tank. It doesn’t make sense for it to be much grander than the main tank.

If I were to choose a size for an average grow-out tank, a 50-gallon or a 75-gallon tank should be good; any bigger is, of course, a bonus. Since the purpose of the grow-out tank is to promote rapid growth for your new fish to achieve a considerable size, then your grow-out tank should be outfitted with all the necessary equipment that promotes the good water quality necessary for fast growth. You should have a fully functioning tank that provides optimum water conditions.

Just like any tank, it should have a good filter that is rated for the tank. It is also expected that the inhabitants of the tank will be fed very well; thus, they will produce a lot of waste matter. It is important to note that aside from an efficient filtration system, a weekly partial water change is required to ensure optimum water conditions.

Why Buy Little Guys?

Your grow-out tank is just another tank, except the inhabitants are juvenile fish. This is so because most fishes for sale in fish stores are juveniles. You can hardly get big fish since these are hard to come by. In most cases, the larger fish you find in stores just grew up in the shop since no one bought them. Adult fish for sale in stores are exceptions rather than the rule. Why are the fish for sale usually small? To answer this, we have to look at how commerce drives the fishkeeping hobby.

For fishkeepers to enjoy their hobby, the stakeholders of the industry have to make money. There are two sources for fish in the Philippine aquarium fish trade: local breeders and importers. These fish are collected by major distributors who sell them at wholesale prices to fish stores; these are then purchased by fishkeepers at retail prices. The key factor is to keep costs to a minimum at all levels to maintain a competitive price that is affordable for the end user: the fishkeeper.

This way, stakeholders earn their living and the fishkeeper is happy. The Philippines, being a tropical country, is ideal for breeding aquarium fish; many of the fish we find in fish stores are bred locally. Live bearers like guppies, swordtails, platies, and mollies are bred year-round in the country. The country also produces many species of cichlids, different varieties of goldfish, carp, gouramis, and catfish, among others. For the fish breeder, keeping costs to a minimum is the key to profitability.

Of course fish breeders incur costs as the fish breed and grow. To keep costs down, they have to quickly raise the newborn fry to a market size acceptable to the distributor. Like they say, time is gold; the longer it takes to grow the fish, the less money they make. Thus, it is expected that fish breeders will sell fish as small as possible because if they grow these any further, they will just incur more costs. Distributors for their part have to buy the locally bred fish at the lowest price possible to keep costs down so they tend to buy these at a low price.

The only way to do so is to buy them small. Imported fish are generally imported directly from other countries. The price of imported fish is dictated by many cost factors: price of the fish, cost of documentation, shipping and handling costs, and brokerage fees. These costs mean that big fish will be more expensive than smaller fish of the same species. Let’s clarify: say that the shipping cost for a Styrofoam box is Php5,000. If you order small goldfish, one styrofoam box can contain 500 goldfish. Dividing PhP5,000 by 500 results in a shipping cost of Php10 per small goldfish. But if you were to order jumbo goldfish, you can only fit 20 per styrofoam box. This results in an additional Php250 for shipping costs alone. Brokerage fees follow the same formula. With this premise, the difference in size resulted in a big discrepancy in additional costs incurred.

To minimize costs, distributors will always prefer to import smaller fish. Therefore, whether your fish is locally bred or imported, chances are big that what you will buy in the fish store is small in size. Now this can be a problem for some buyers. If you have been keeping fish for some time, chances are, your fish have grown and buying a small fish can pose the problem of where to keep it. When the fish of your dreams suddenly appears in your favorite fish store, I bet you will be antsy and eager to bring it home. But without a grow-out tank, where to put it is a major concern. Some fishkeepers divide their tanks using glass panels held up by suction caps.

This seems logical so long as the tank is big enough to hold both sets of fish, and/or none of the fish decide to go to the other side. In extreme cases, impulse buys result in fishkeepers throwing the new arrival in the reservoir chamber of the sump filter. While it may survive, this is not a good home for the fish. All these hassles will be avoided if you have a grow-out tank. It does not need to be a high-end one; a simple but fully functional tank can serve this purpose. Your grow-out tank should give you as much pleasure as your other tanks since it will have the fish you’ve always wanted, and they will be part of the collection you will be proud of in the not-so-distant future.


This appeared in Animal Scene’s February 2016 issue.