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Stuck with a Common Pleco?

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This is an article about how to deal with a common pleco if you keep one with your goldfish out of misinformation or lack of knowledge before purchase.

The common pleco is one of the most commonly sold varieties of plecostomus at most LFS. With that, many of us end up buying one of these fish that we think will conveniently keep our tank algae free.

Eventually we are hit by the realization that the common pleco grows to be a fairly large fish, produces a large amount of waste, and clearly is not satisfied by the algae that may or may not naturally grow in our aquarium.

I have been there, and done that, and the following post is based on my personal experience over the past five years as well as reading up a lot about this on various pleco forums:

A. If you can, stay away from the common pleco before you buy one. There are other plecos that do well with goldfish, and I will get into that in a little bit.

B. If you have a small common pleco and can still return him to the LFS, return him if you are ok with that decision.

C. If you have a common pleco with your goldfish, and you also have at least a 55g tropical tank to move him into, do that but make sure to slowly transition the pleco to the new water parameters (temperature, pH etc).

If none of the above applies to you, then keep reading for some helpful information:

Common plecos are some of the largest fish available at most LFS. These fish can grow to a length of up to 24+ inches, although the average size seems to be at around 11-15 inches in an aquarium, unless your tank volume is in the three-digits.

This is similar to any breed of goldfish, who all have the potential to grow to a body length of 8-12 inches if enough space and food is provided.
The minimum tank size to keep these guys in is 55 gallons. Ensure to provide at least the same amount of water volume per pleco as you would do with goldfish (ideally a minimum of 150% of that amount), or be sure that you will do a lot of water changes on his tank.

Common plecos are generally peaceful fish. They are for the most part nocturnal, and in order to be comfortable during the bright day time, they require hiding spaces such as larger pieces of drift wood (most recommended) or artificial caves, plants etc.

A common pleco in a completely bare tank with just a couple plants will become stressed out over time and is more likely to display aggressive behavior.

Due to their nocturnal nature, they enjoy not only hiding places, but also dark substrate to aid their camouflage coloring. There is a reason they have this dark and light camouflage pattern.
My current tank has a few hand fulls of dark substrate along with two pieces of drift wood and a bunch of dark brown and black large river rocks either placed on the bottom of the tank, or with tall anubias tied to them, or several rocks siliconed into small, tall formations for additional cover.

Their natural habitat are streams and rivers, and they enjoy stronger current. Overfiltration (10x tank volume per hour or more) is definitely recommended. Mine loves to swim downwards in the current of the bubble wand powered by a Whisper 300, in addition to 770gph HOB filtration in a 55g tank, along with an Aquaclear 20 Powerhead (127gph) placed as close to the bottom left back corner of the tank as possible.

The common pleco's natural diet consists mostly of algae during their early time. Of course since they grow to be rather large, algae alone will not suffice. They begin to eat decaying plant material as well as decaying bodies, such as sick or dying fish.

This is where one of the "myths" come from that a common pleco will attack your goldfish because the goldfish's slime coat is tasty.

The truth is this:

Yes, they will attack the goldfish because the goldfish's slime coat is quite nutritious.

But this happens due to the fact that a large fish like the common pleco will have a tough time competing with goldfish, especially considered that the pleco is mostly nocturnal. Often, a pleco kept with goldfish will starve to a degree.

As we know, goldfish are little pigs and they will immediately gobble up pretty much anything edible you drop into the tank.

Plecos, being nocturnal, won't always come out to eat when food is served throughout the day, as it is mostly against their nature. Aside from that, even if they get past their shyness and try, the piggish goldfish are more than likely to have consumed most of the food that was provided.

Even if you feed algae wafers for bottom feeders, chances are 9.5 out of 10 that your goldfish will have eaten most of that before the pleco even dares to approach the food.

"Attacking" other fish happens due to the fact that as the common pleco grows older and significantly larger, the little bit of algae alone is not enough to sustain these fish. They do crave some protein too, and I like to toss a generous pinch of goldfish pellets into the tank every night just before I go to sleep. A lot of it will still be eaten by the goldfish, but in the dark the pleco is more likely to forage for stray pellets.

Gel food such as homemade or Repashy Soilent or Super Green work great too, but you will have to feed a considerable amount because the goldfish will want to gobble up as much as possible. Again, a good amount of gel food fed a couple hours after the tank lights go off will significantly help the pleco in finding enough food.

In addition to that it is highly beneficial to have some blanched vegetable available in the tank most of the time. This won't be gobbled up by a goldfish within minutes, but usually lasts for hours or even a couple of days, depending on how much vegetable there is vs fish and how much other things you feed.

Peeled, (seeded), blanched zucchini, cucumber, spinach and kale, or other green vegetables are almost always available in my tank. That way the pleco can eat over night with being disturbed by the goldfish.

Another reason for common plecos (or even small plecos) to "attack" your goldfish is disease or injury.

In nature, plecos are somewhat of a cleaning crew. Reducing algae, eating decaying plant material, and consuming diseased or dead fish is all in their nature. Keeping an ill or injured (gold)fish with any kind of pleco poses a serious threat to the health and live of the affected fish.

Should one of your (gold)fish be ill or injured, always make sure to QT them away from any other fish! We have even seen cases where even mellow (gold)fish would start eating on their still living but ill or injured buddy, causing (further) injury or even the death of the affected fish.

Driftwood.

Most varieties of plecos require submerged wood. They will graze on it and consume some of the fibers which are beneficial to their digestion.

Aside from that, as mentioned above, a properly sized piece of driftwood will offer cover to an otherwise stressed and aggressive fish.

Keep in mind that as your common pleco grows you will have to offer larger hiding places.

Not too long ago, my own pleco started to be somewhat stressed out because the smaller piece of wood and the few pieces of anubias would not provide proper cover for him any longer, and he would freak out several times a day, dashing about, and darting to the surface. And if there wasn't a cover he might even have even accidentally jumped out of the tank.

I then ordered another piece of wood as well as a bunch of tall anubias, added a medium sized clay pot laying sideways and made small "walls" out of up to 5-6 pieces of kid-fist sized dark river rocks.

Since the addition of these things he has not freaked out at all, even with the lights on.

So yeah. If you can, stay away from adding common plecos with your goldfish, until you have a very large (100+ gallons) tank availabe, and still make sure to keep the pleco as comfortable as possible.

As for the smaller varieties of plecos (under 6-8 inches) that usually can live with goldfish without problems (if you provide enough food and keep sick goldfish away from the pleco), here is a quick list of the most commonly available plecostomus varieties:

Bristlenose Pleco

Rubbermouth Pleco aka Rubberlip Pleco aka Bulldog Pleco

Clown Pleco

Royal Pleco

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Great post!:-) I have 2 Bristlenose plecs in with my goldfish!! no problems at all!:-)

I have a clown pleco in my tropical tank!...beautiful fish but painfully shy!....never see him!!:-(

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This looks like an article to me. Nice job, Fang.

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Nice job, Fang! :)

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Great post, very useful information. Thanks :3

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Great post!:-) I have 2 Bristlenose plecs in with my goldfish!! no problems at all!:-)

I have a clown pleco in my tropical tank!...beautiful fish but painfully shy!....never see him!!:-(

I see the same thing with my own clown. He is the shiest pleco I ever had (common, rubberlip, bristlenose and clown) and I often don't find him for days, even if I am actively looking for him. I actually am checking weekly if I may find his dead body somewhere, no joke :lol

But hey, I always find him alive and happy, but hidden under plants or the drift wood. He is even growing bigger, so I know he is doing well. :)

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Great post!:-) I have 2 Bristlenose plecs in with my goldfish!! no problems at all!:-)

I have a clown pleco in my tropical tank!...beautiful fish but painfully shy!....never see him!!:-(

I see the same thing with my own clown. He is the shiest pleco I ever had (common, rubberlip, bristlenose and clown) and I often don't find him for days, even if I am actively looking for him. I actually am checking weekly if I may find his dead body somewhere, no joke :lol

But hey, I always find him alive and happy, but hidden under plants or the drift wood. He is even growing bigger, so I know he is doing well. :)

I haven't seen my clown pleco for months!! I drop an algae pellet in before bed! and its gone by morning!!:-)

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great article! :)

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Even when I've had sick fish, none of my bristlenose ever tried to harm them. I even had a bottom sitter and all day and all night the bristlenose left that goldie alone.

As for a common pleco, very cool write up!

Edited by Acro

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Nice! I accidentally got a common pleco, who was badly bullied by my goldfish and I ended up removing him from their tank and eventually taking him to the pet store to be rehomed.

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Just a few comments on the common pleco I did not see mentioned in the opening post (sorry if they're there and i missed 'em):

Common plecos reach 24" in length if they don't die of starvation, stunting, or poor water quality first-most common causes of death. 

Common plecos needs 200g+ tanks when full grown, its best to get them in a big tank asap!  A 55g tank is only good maybe through 10-12", they need a long that's wide enough to turn around in.

Keeping a common pleco (or any large breed pleco) in a 'small' tank will stunt their growth-body won't grow but organs still do.. this can lead to a painful death.

Big pleco means BIIIIIIIG POOOOOP!!! They can have turd strands over 4x their body length!  This leads to a messy tank/clogged filter very quickly!  Keep up on large water changes and siphoning out poop frequently (daily or at least 2-3x a week)!

 

 

Side note:

Leopard sailfin pleco (petco sells as 'Columbian pleco') get to 18" and need 175g+ when full grown.  I had one that ate any plants in the tank (had to use aquaponic system to help with nitrates) and clogged my sun sun canister filter.  I tried the largest ehiem on the market I could find, pro 3x something and the pleco even clogged that one up!  This was with every other day water changes.  I finally had to rehome it as I was breaking my back with all the water changes!  Fortunately found a him a good home with a huge tank and good filter (sump).

 

 

IMO you're better off getting a mystery snail or large nerite snail instead of a pleco to clean diatoms.. hell I prefer my 'pest' snails (pond, bladder, and ramshorn snails) over plecos.

Edited by AquaAurora

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The largest common pleco I had was 12 inches. However I did see one that was raised in a pond and it was three foot.  The one I have now in my 75 gallon is growing but kind of slow. Soon as he is to big for Willow to eat he well go in the 150 gallon tank.   

Yes they are supper messy.

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They have one at the zoo that is the biggest on I have ever seen... Got to get a photo next time :o

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Keeping a common pleco (or any large breed pleco) in a 'small' tank will stunt their growth-body won't grow but organs still do.. this can lead to a painful death.

 

Thank you for an excellent discussion of common plecos.  

 

However I have to point out that that the quote above is one of those myths that gets repeated so much on the internet that people assume it is true.  No biological process exists that would have internal organs  grow while the rest of the fish does not.  

 

Stunting is a real phenomenon in animals, including humans.  Usually caused by malnutrition in early life, whether from lack of food, disease, parasites, or severe crowding or other physiological stress, stunting does not produce ill health if the conditions that caused it get corrected.   In fact, if you look at the goldfish that have set records for longevity, you will see a bunch of stunted goldfish, whose owners proudly tell you how careful they were to not overfeed the fish when it was young (just a tiny pinch of food daily).

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My gold fish jump out of the tank and injured. After returning it to the tank the pleco was very aggressive like never before. It started biting injured gold fish and injured one is dead after 10mins.

 

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