Which algae eating Pleco???


Retired Staff
Apr 8, 2009
So many people ask 'What is a good pleco for keeping algae down in a fish tank?'
I've written this guide which will hopefully help answer the question and also help avoid getting large plecs that are not suitable for the average size aquarium.

Here is some info, care requirements and photos for 4 top algae eaters.

1. The common pleco.

There are a few pleco's that are given the 'tag' common pleco, the two i'm providing info about are the most likely 'common' plecs that you will see in the LFS. These are two very similar pleco's, the L021,L023 Pterygoplichthys pardalis and the Pterygoplichthys disjunctivus.

The pardalis and the disjunctivus are excellent algae eaters especially when they are young, the downside is that they both grow to over 1 foot long in quite a short time, most certainly under a year given the right care requirements. This plec really is unsuitable for most aquariums due to the space it needs to grow and be happy.

How can i tell that the cute baby pleco at the fish shop is going to grow up to be so big?
Have a look at the dorsal fin(the fin on the top of the plec). If you count the rays and they add up to more than 10, then it is very likely the pleco is a Pterygoplichthys and all the plecos in this family grow to be very large.

How can I tell the difference between the pardalis and the disjunctivus?
There isn't really much difference apart from the pattern on the tummy. The pardalis has a spotted pattern whereas the disjunctivus has a vermiculated pattern. See pics below

How do I sex my common pleco?
I have read from various sources that large males have thickened pectoral fins that can have a red looking colour to them. The other way is to inspect the genital papillae.

I heard that common plecos catch and kill smaller fish or suck the slimecoat on my other fish, is this true?
The only way that this would ever happen imo is if the pleco was starving and desperate. They will most certainly feast on a dead fish or even a dying fish given the opportunity but this is true of most fish.

Care Requirements

Tank Size: Unless you are willing to upgrade within a couple of months, then this pleco isn't suitable at all for small or medium sized tanks. It really requires at least a 5 or 6 foot tank.

Water parameters: Not too fussy about the PH- Anything between 6 and 7.8 should be fine. Also the same with the GH. Temp should be between 21c and 26c

Feeding: This plec is an omnivore and even though will eat the algae in tank, it also need to have other foods provided. Veggies, algae wafers and occasional meaty foods should be their diet.

Max growth size:Almost 1.5 feet but commonly averages around 1 foot or slightly larger.

Breeding: Highly unlikely in an aquarium

Temperament: Generally pretty chilled but can get territorial over space and food with similar sized plecs, especially in smaller tanks. To keep two of this size would really require a tank size of 125(uk) gallons+ imo.


Pterygoplichthys disjunctivus

The tummy pattern

Pterygoplichthys pardalis



2. Chaetostoma sp.1 L187b
aka rubbernose, bulldog plec

There are various chaetostoma available, some have higher care requirements than others. Im concentrating on one of the more commonly available and easiest to keep, the L187b. These guys seem to get overlooked, maybe because they are very difficult to breed or require lower temps than most other pleco's, I know if I saw one in a fish shop I would be very tempted to buy it.

They aren't as hardy as either the 'common' pleco or the 'common' bristlenose so not really ideal starter pleco's but would make a great addition to a tank for people that have advanced past the many issues often experienced by new fish keepers.

In the aquarium they would like rounded pebbles and plenty of oxygen

Care requirements

Tank size: 60 litres+

Water Parameters: ph 6.8-7.8, plus they do like the water to be a little on the hard side. Temp should ideally be kept under 24c, they also require well oxygenated water.

Feeding: An omnivore that would really need some algae around the tank. They will also eat veggies, algae wafers and some meaty foods.

Max Growth: 4.5 inches.

Breeding: Have been bred in an aquarium but fairly difficult.

Temperament: peaceful but can be territorial with conspecifics.

For more info and a great article---see here Meet the Rubbernoses


Permission to use photos very kindly given by Xingu.

Source for care requirements came from here


3 Ancistrus cf cirrhosus
aka the 'common' bristlenose

I think the title for the best algae eater should go to the common bristlenose, it really does tick all the right boxes when looking for an effective smallish algae cleaner/eater. There are various other ancistrus available but as with the chaetostoma some have higher demands and care requirements plus the common bristlenose is usually easily available. It is best to research if you require any of the other bristlenoses.

Very undemanding which make the 'common' bristlenose an excellent introduction to the world of plecos, also one of the easiest to breed.

How do I sex a 'common' bristlenose?
Fairly easily. Males will start to grow bristles round the nose, they will also grow bristles up the middle of the snout, from the middle of the lip that almost reaches the top of the head. Females can and often do produce bristles round the nose but never up the snout. Males in my experience tend to be slightly larger than females. Male ABN ( albino 'common' bristlenoses) develop a red patch on the top of the head.

Care requirements

Tank size: Absolute minimum 50-60 Litres

Water parameters: Not fussy, a PH anywhere between 6 and 7.6 would be fine. Temperature should be between 21c-26c

Feeding: An omnivore that needs addition food in the tank other than algae. Veggies, algae wafers and occasional meat should be provided. Wood can also be provided for bristlenoses to graze on. There is a theory that lignin that is available in wood could be part of a bristlenose's diet due to the length of the gut but has not yet been proved.

Max Growth Size: Around 5 to 6 inches

Breeding: fairly easy

Can be territorial with conspecifics especially if the tank size is too small or not enough hidng places are provided.


Pic 1,2,3 Male 'common' BN--white tips on dorsal fin and tail fin

1st pic is a female ABN and a L144
2nd pic Male ABN
3rd pic Male ABN


4 Otocinclus

There are a few oto's that are fairly easy to come by ie vittatus and affinis. They really need to be put into a well established tank with lots of brown algae and excellent water conditions. Whilst they are fairly hardy they are sensitive to waste build up, so any traces of ammonia and nitrite are a no no and nitrates need to be kept low, all other organic waste should be kept to a minimum with good filtration and regular water changes. They will also not do well in tanks that are over clean as they need a supply of algae.

Care Requirements

Tank Size: 30 litres+, remember that the smaller the tank, the easier it is for the tank to have waste build up.

Water Parameters: Not overly fussed about PH, hardness and temp but will not tolerate poor water conditions. They also need the tank to be very well oxygenated. Well established planted tanks are ideal once they have been acclimatized.

Feeding: They really need algae in the tank, plus sinking pellets, spirulina tabs, veggies such as spinach.

Max Size: 5cms

Breeding: Have been bred, theres a Breeding Report here Otocinclus vestitus

Temperament: Peaceful and need to be kept in groups. Can be shy but not as nocturnal as other catfish.


Otocinclus Vittatus

Photo belongs to smithrc

Thank you to Brengun for permission to use the above 3 photos.

For further information concerning oto's check out this link especially 'acclimatizing oto's to the planted aquaria' section.

Little Monkeys in the planted Aquarium

Reference and some care info came from here


All in all, thats my top 4 Algae Eating Plecs, hopefully this article will help some people and especially help to prevent buying totally unsuitable fish.

Written by Lisa aka Doodles
Please do not copy or reproduce this article or photos without permission first.