Be careful of that label!

Why research is always needed before a fish purchase

When the average first time aquarium keeper walks into a pet store, they completely trust the employees there. Sometimes that trust is well placed, and the budding aquarist walks out with a 29 gallon (109 L) tank, some lovely X-ray tetra (Pristella maxillaris), and a water parameter testing kit. Other times, the new (and soon to be disappointed) aquarist walks out with a 20 gallon (75 L) tank, a pleco, an oscar, and—worst of all—a black ghost knife fish. (If you didn’t cringe at that, don’t worry, you soon will.)

In this particular article I’m going to be using Petsmart and Petco as examples simply because I know these stores best. They are the large chain pet retailers that I have closest to me. This is in no way intended as a stab at these stores because while there is a lot of bad information, they also have some proper information on the labels of the fish they sell. I am highlighting particular instances where the label is grossly wrong as an example of why research is needed or you may end up with more than you bargained for.

Clown Loach (Chromobotia macracanthus)

As adults, the vibrant colors of clown loach fade (Public Domain)

I’m going to start with my favorite fish of ones I’m highlighting today: the clown loach. Entertaining and active, these guys would make a great addition to your home aquarium, right? Wrong. Like so many of these tankbuster species, the little clown loaches you see at the store are babies. Probably less than a few months old. Now let’s compare Petsmart’s and Petco’s care advice for these species versus the advice from the loach experts over at Loaches Online.

	Loaches Online	Petsmart	Petco
Min tank size	180 gal (680 L)	40 gal (150 L)	50 gal (190 L)
Adult Size	12 inches (30 cm)	12 inches (30 cm)	12 inches (30 cm)
Hardness	1-12 dGH	NOT SHOWN	NOT SHOWN
pH	6.5 - 7.0	NOT SHOWN	6.0 - 7.5

As you can see there are some major discrepancies. Loaches Online’s veteran clown loach keepers recommend the smallest tank juveniles (which are what is sold in stores) be housed in is a 55 gallon (208 L) tank with biweekly water changes because these fish are active swimmers and any less will cause stress and stunting, but this should only be temporary housing. And the fact that some of the parameters such as pH and hardness aren’t even given in the Petsmart and Petco labels is also unsettling as the wrong pH and hardness can stress a fish to death. Sadly, I found this to be a constant with the Petco and Petsmart labels. Another surprising constant I found through the Petsmart and Petco care sheets was proper temperature for these fish, but this is only part of what is needed to keep a fish healthy. You can’t complete a puzzle without all the pieces.  

Fortunately, if you like the look of this fish there are some loaches that stay small enough to fit in the average home aquarium. The yoyo loach (Botia almorhae), angelicus loach (Botia kubotai), zebra loach (Botia striata), and Burmese loach (Botia histrionica) all have a similar shape and personality to the clown loach. If you search by the scientific name, you can find pictures of these cute, colorful fish. The only difference between these guys and the massive clown loach is that these guys can safely live their complete lives in a 50 gallon (190 L) tank which is a much more common and manageable size home aquarium.

Pleco, Plecothemus (Hypostomus plecostomus)

Mature pleco (Derek Ramsey @ Wikipedia)

The main reason people buy this fish is for its algae-eating abilities (I will go into why this is bad in a later article). Yes it does eat algae when small, but as it grows it begins to also eat lots of protein. This can easily mean small fish; it has also been known to attach to larger slow-moving fish like goldfish (Carassius auratus auratus).  Let’s compare what the expert fish keepers over at Tropical Fish Keeping.com have to say about plecos versus the Petsmart and Petco labels.

	Tropical Fish Keeping	Petsmart	Petco
Min tank size	55 gal (208 L)	55 gal (208 L)	10 gal (38 L)
Adult size	20 inches ( 50 cm)	24 inches (61 cm)	24 inches (61 cm)
Hardness	Less than 28 dGH	NOT SHOWN	NOT SHOWN
pH	6.0 – 8.0	NOT SHOWN	NOT SHOWN

While Petsmart did get the sizing right, I still see the associates selling these fish to anyone who asks for an “algae eater.” On the other hand, Petco falls very short here. Pleco need large tanks not only because of their size but also because they produce a lot of ammonia relative to body mass. They are comparable to goldfish in the amount of fecal matter and ammonia they produce. Again, neither of the chain stores mentions hardness or pH, two essential elements for keeping fish healthy.

Fortunately if you like the look of plecothemus, it has some relatives that can easily fit in your aquariums. The bristlenose pleco (Ancistrus sp) is similar in appearance and behaviour but only grows around 4 inches (10 cm) long. A single individual can be housed in a 10 gallon (38 L) tank or a pair in a 20 gallon (75 L). Groups need a 50 gallon (190 L) or larger tank as males can be territorial.

Black Ghost Knifefish (Apteronotus albifrons)

Juvenile black ghost knife fish
(Derek Ramsey @ Wikipedia)

While this is an interesting and unusual fish, this is a fish best left to be admired in public aquaria. Due to its large size, timid nature, and unique biology, this is not a good home aquarium fish, but it is still sold as such. Let’s compare Petsmart’s suggested care to a knowledgeable fishkeeping site’s care.

	Tropical Fish Keeping	Petsmart
Min tank size	180 gal (680 L)	75 gal (284 L)
Adult size	20 inches (51 cm)	20 inches (51 cm)
Hardness	5- 15 dGH	NOT SHOWN
pH	6 – 8	NOT SHOWN

Due to the manner in which these fish use electricity, their spines are inflexible. They must have an aquarium that is at least three times its length and twice as wide as the fish is long.  A regular 20 inch (51 cm) fish could hardly fit in a 75 gallon (284 L) aquarium let alone a fish with an inflexible spine. As with so many other species, Petsmart is falling very short on its care. At least Petco doesn’t carry this species.

For those looking for an alternative fish that still maintains the strange look of a knife fish, the African knifefish (Xenomystus nigri) is a good alternative that can be housed in a 55 gallon (208  L) tank. As all knifefish are rather delicate, this fish is not for the beginner aquarist and should be housed in a specialized setup. It is not for your typical community tank. Extensive research is suggested before buying this fish.

Pangasius catfish (Pangasius sanitwongsei)

Adult captured in Thailand (Matt Leete @ Fishbase.org)

Sometimes sold as an iridescent shark or paroon shark, they may look cute as babies at the store, but this is a species that is wholly unsuited for even public aquaria. A close relative of the massive Mekong giant catfish (Pangasianodon gigas), one of the largest freshwater fish in the world, any store that sells this fish and claims it can live comfortably in a home fish tank should be ashamed. This is a massive migratory and skittish species known for slamming into the tank walls when frightened. With specimens tipping the scales at 660 lbs (300 kg), a single fish could easily crack or break a tank wall.

	Seriously Fish	Petsmart
Min tank size	500 gal (1892 L)	75 gallons (283 L)
Adult size	48 inches (1.2 m)	25 inches (61 cm)
Hardness	2 – 30 dGH	NOT SHOWN
pH	6.5 – 7.5	NOT SHOWN

As you can see in this case, Petsmart falls very short of the care requirements of this species. Practical Fishkeeping is part of a movement called The Big Fish Campaign to spread awareness about this species and the other tankbusters like the tiger shovelnose catfish (Pseudoplatystoma spp), red tailed catfish (Phractocephalus hemioliopterus), and giant gourami (Osphronemus goramy). If you buy this fish and think you will just get a larger tank as it grows, think again. This species is known to live for 20 or more years and will need a tank as large as a medium moving van. And most public aquaria won’t take them when they outgrow your tank. This species is beyond their capacity to house long-term.

As you have seen, these two major pet retailers fall very short on their care sheets for these species. Many of these care sheets also cite the “gallon per inch of fish” rule which aquarists have known to be a poor stocking tool for a long time. Think about it this way, 10 inches of neon tetra aren’t the same as 10 inches of oscar. The 10 inches of neon tetra could easily be kept in a 10 gallon tank, but a 10 inch oscar would hardly be able to turn around. This rule doesn’t hold water when looking at fish larger than an inch or two because it doesn’t take into account the fish’s depth as fish grow in three dimensions, not just one. To be safe, I wouldn’t stock any tank based on this “rule.”

The only rule you can use to stock a fish tank is research, research, research. I hope these comparisons have opened your eyes to the need for it. I know there are many people who instinctively trust retailers, but as you have seen they cannot always be trusted to give you the correct information on your fish and in many cases are just trying to make a sale. In fact, telling you a fish needs a smaller tank that it should be housed in will cause the fish stress; stress leads to disease; and diseases are cured by medication bought from the store. See a pattern here? Always research before you buy!

Works referenced

Craig, Nicolette. 24 March 2011. “Who’s to blame for the big fish problem?”  www.practicalfishkeeping.co.uk. Retrieved 11 May 2012.  

Gay, Jeremy. 27 January 2012. “Will you support the Big Fish Campaign?” www.practicalfishkeeping.co.uk. Retrieved 11 May 2012. 

Hill, Nathan. 8 March 2012. “Where do all the big fish keep going?” www.practicalfishkeeping.co.uk. Retrieved 12 May 2012.

Monks, Neale. 2009. "Knifefish in the Aquarium." Tropical Fish Hobbyist (June): 86-90.

Fish Profiles referenced on 14 May 2012:

Clown Loach

• Petsmart
• Petco
• Loaches Online

Plecostomus

• Petsmart
• Petco
• Tropical Fish Keeping

Black Ghost Knifefish

• Petsmart
• Tropical Fish Keeping

Pangasius Catfish

• Petsmart
• Seriously Fish