Diamond Watchman Goby: Size | Diet | Breeding

There are so many factors that determine how fascinating your aquarium can be and one of these factors includes the kind of fish you put in it.

There are numerous types of fishes that can amplify your fish tank’s appearance, and one of them includes the Diamond Watchman Goby which is also known as the Maiden Goby, the Orange Spotted Diamond Goby, the Orange-Dashed Goby, and the pretty pawn among many other names.

This fish will not only ensure that your fish tank looks remarkable, but will also make it interesting to look at and will add character to it.

Personally, I find them very attractive and fascinating to watch, I can spend hours watching them dart around the gravel moving substrate and creating their home.

I had never come across them until a friend suggested them to me, and I thought it was a good idea to have such a pretty fish in my first aquarium. Ever since, I have been a huge fan of these pretty pawns and I have always considered having them in every other aquarium I have bought since.

Let’s take a closer look and see if one of these fish would be a suitable saltwater fish for your aquarium, and if they are, let’s see what you’ll need to provide for them to thrive in your home aquarium.

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Origin & Habitat

The first time Diamond Watchman Goby came to the attention of the aquatic world was in 1956. This was after Tomiyama discovered them in the Indo-Pacific Ocean. The Indian Ocean is home to a vast selection of marine life with more than 3000 species compared to the western Atlantic which has 1500.  

Its beauty has ever since fascinated fish tank lovers all around the world and now you can find them in any part of the globe amplifying the look of aquariums with their beauty.

Fact: Diamond Watchman Gobys latin name is Valenciennea puellaris and they are native to the Indian Ocean and Western Pacific Ocean

These fish exist in different parts of the world including East Indian Ocean, West Indian Ocean, and Australia. This fish is always up to something, which is what makes it much more entertaining than a lot of other saltwater fish. In the ocean and on the reefs, the Diamond Goby can be found usually in pairs and they are thought to be monogamous. They can be seen digging burrows in the sand bed where they will rest at night or retreat to at the first signs of danger.


The first thing that you will notice with the Diamond Watchman Goby if you look closely, is its incredible looks and the amazing details. Without a doubt, the diamond watchman goby fish is among the most beautiful goby available to aquarists.

FACT: The biggest Diamond Watchman Goby recorded in the wild was over 8″ but the average adult in a home aquarium is 6-7″

Their heads are rather large in comparison to other parts of the body, and they also possess interesting large jaws that are usually cyan colored. It is impossible to miss them even with a bunch of other brightly colored and interesting tank mates. This is why Diamond Watchman Gobies are usually great whenever it comes to making a fish tank attractive, colorful and unique. They certainly add character and dynamics to any aquarium. 

Watchman Goby Size?

It might be one of the reasons why they are also referred to as pretty pawns. They are usually around 6” long with a maximum length of 7 inches. This is a great size for a nano aquarium and a community or reef tank.

They usually have an orange/yellow stripe running from the head of the fish all the way to its tail. You will be even more impressed with their colorful eyes and their fascinating fins. Their eyes just seem to pop out and catch your attention.

Diamond watchman goby

What size aquarium do gobies need?

The Diamond Watchman Goby should be housed in an aquarium that is at least 55 gallons and if possible a wider aquarium than deeper. This will give them the best environment required to create and mark territory and make a nice, deep burrow for them to live in.

Diamond watchman goby is known to be very active, and that is why it needs a tank that has a strong refugium or sump as well as to ensure they get the best water conditions and provide them with a constant supply of copepods to feed off.

You should also ensure that you fill the aquarium with a deep layer of fine sand which is usually the biggest component of their natural environment. If you build a rock display in your tank, see to it that they are firmly held in place with tank safe glue or silicone.

FACT: Due to these fish burrowing in the substrate you’ll need at least 3-4″ of soft sand in your aquarium

This is because Diamond watchman gobies are known to be very good when it comes to sifting the sand so as to capture and feed on small micro-organisms that usually hide within the sand. This will tend to cause instability, and if the rocks are not firmly in place, they may eventually shift position; a move that might end up to be very dangerous to both the pretty pawns and other fish inside the aquarium.

You can also push the rocks deep into the sand with its base at the bottom of the tank. This will definitely help give it the stability required to keep your Diamond watchman gobies safe.

Another main factor that I feel you should consider before placing Diamond watchman gobies in a tank is the filter capability. These fish require and deserve, like all other fish, the best possible water conditions. We have reviewed some of the best external canister filters combined with a large refugium tank which would give them the best possible water conditions. 

It is worth mentioning these fish can jump! They are known for leaping out of the aquarium to their death even after they have settled into life in their new home. You think they are settled in and then you find them the next morning on the floor.

Ensure you have a cover on the top of your aquarium, many reef tanks have a made to measure stainless steel sheet on top to prevent your fish jumping out but still allowing light to enter the aquarium.

Sand shifting goby care

Scientific NameValenciennea puellaris
Common NamesPretty Prawn Goby, Orange Spotted Goby, Maiden
OriginIndian Ocean,Indonesia, Sri Lanka, Vanuatu,Fiji
Water Conditions73-78° F, dKH 8-12, pH 8.1-8.5, sg 1.020-1.025
Care LevelEasy
Reef CompatibleYes
Max Size6-7"
Tank Size55 Gallons+
JumpersYes, Lid/Hood needed
Ideal first fish?Yes
Suitable FoodsFlake, live foods,copepods,mini sinking pellets
suitable Tank MatesShrimps, Clownfish, Dwarf Angelfish, Wrasse, Damsels,Filefish
Desirability High

It is mandatory that you always check the water conditions required before you place any fish in water. This is because if you don’t meet the specific conditions, you may end up killing every fish in your aquarium or causing them longterm suffering.

This is totally unacceptable! As a responsible aquarium owner we have a duty of care to our fish and providing each species with the correct environment and water conditions is paramount.

I usually advise first-time aquarium owners to be very keen on this part of the hobby which can be overlooked when they first start an aquarium.

FACT:Natural enemies of goby are large species of fish and even birds in shallow freshwater species

Your Diamond watchman goby will need to have a PH of 8.1 to 8.5. You should also maintain the water temperature at 73F to 79F. Among other things that people usually ignore is the water specific gravity which should be 1.020 to 1.025 and the dKH 8-12. These are the optimal water conditions that make Diamond watchman goby feel at home and thrive. 

You will need to perform a partial water change at least once every two weeks and we recommend 25% of the water should be changed. To ensure you keep the nitrate levels down we also recommend you fill the aquarium using RO-DI water.

You can purchase RO-DI water from your local aquarium store or use an RO-DI unit to ensure your tap water is filtered to give your fish the best possible water. 

What do you feed a watchman goby?

Diet is yet another critical factor when keeping the Diamond watchman goby. This is because the diet needs to be varied enough to give your fish all the nutrients and protein they need, otherwise they will end up starving to death.

This is a sad factor with many picky eaters in the saltwater aquarium world. Thankfully this is not a big issue with this fish and they will readily accept most foods and particularly like live foods including copepods and brine shrimp.

We have reviewed some of the Beginners Guide to tropical and saltwater fish food in another article, we have included the link.

You should also ensure that you keep the feeding schedule which should be 2-3 times a day in small portions. Feeding your Diamond watchman gobies too little or too much (which can be equally as destructive) can have devastating consequences.

FACT: Diamond Watchman Gobies are Carnivores and will accept most foods. However, ensure they get a share of the food before the surface feeders eat it all.

Do Diamond Gobies eat copepodes?

These Gobies are known to scoop up a chunk of sand in search of tiny invertebrates which they filter through their gills. They are known to eat Zooplanktons such as Copepods and Cyclops.

You can also feed them small crustaceans that include Mysis, artemia, and krill among many others. These foods will supply them with the nutrients needed to keep them fit and healthy.

Depending on the other fish within the aquarium, these fish can often miss out on food as the other faster-feeding fish eat all the food before it has time to drop to the bottom of the aquarium where the goby is sat waiting for its lunch.

You can use certain methods of feeding which can ensure that they do get a share of the food. You can use a feeding stick and wave the food in front of their burrow or hole or use a turkey baster to blast live food directly into their area. This will see to it that the gobies are well fed and don’t miss out.

If you’re wondering what’s the best time to feed saltwater fish then read our guide on this topic. We have included the link for you.

Tank Mates You Should avoid

Having one kind of fish in your aquarium is very boring and offers little in the way of entertainment. It tends to make the environment feel sort of artificial which is not the look and feel that saltwater fishkeepers want.

A good aquarium should look natural and vibrant in color and have a lot going on to keep you entertained. This is why you are always advised to mix up the fish and invertebrates in your aquarium. This is not just done by taking any type of fish and adding them into your aquarium. You might end up accidentally feeding your small fish to the big fish without knowing.

You should thus be very keen to know which species of fish can coexist together. This will enable you to know which species to add and when to add them, which is equally as important to prevent bullying and being territorial. It will also help you to have a calm aquarium with every fish living harmoniously without any problems.

FACT: There are over 2000 species of goby fish and over 100 are available to the home aquarist.

These fish can live with a wide variety of fish and I have kept them successfully with Dwarf Angelfish, Pink Fairy Wrasse,  Foxface Rabbitfish, Cleaner Wrasse and Clownfish. These are just a few saltwater fish that I have kept with a Diamond Watchman Goby without any problems what so ever.

The only thing you should avoid is adding other sand shifters or gobies into the aquarium as they can become very territorial and will defend their area with force. 

One of the best relationships you will see in an aquarium, apart from maybe the clownfish and anemones, are shrimps and gobies. They live together and form a bond like no other marine creature. They live together, defend each other and search for food like a dream team. You have to see this in action to believe it. 

( This Image shows the perfect relationship between Goby & Shrimp )

Sexing & Breeding

If you want your Diamond Watchman Goby to breed, you will need to ensure that you pair them up which is the hardest part. The Diamond Watchman Goby is a protogynous fish which can easily change gender when needed and housed in an aquarium with a number of gobies they have the ability to change sex in order to pair up. 

They will pair up easier if you have a number of differently sized gobies which makes pairing easier.

You will need a specialist or your local aquarium store to help you determine the male and the female gobies because their physical appearance doesn’t tell you which is which. Their breeding technique is usually simple. The male and female usually position their fertilized eggs on top of the burrow.

FACT:Gobies are able to change their gender and transform from females into males and vice versa.

To ensure that nothing happens to the eggs, the male will keep guard for at least 3 days after which the eggs will hatch to larvae.

The tricky part is after breeding because the larvae which are also known as fry are required to be fed fine food such as planktons. Buying planktons to feed them can be very challenging and hard to find. Not all aquarium shops stock it. Remember that if you don’t feed the fry enough, they may not get the required nutrients to grow and often die very shortly after birth. 

The young fry will attract a lot of attention and will be eaten by other fish if not removed from the main aquarium. You may be lucky leaving them in your main tank to grow but the survival rate is almost zero. So we highly recommend you remove them into quarantine or separate tank to feed and grow in peace. 


  1. How long do Watchman Goby live for? Answer: On average in the home aquarium 4-6 Years. In the wild, they have been known to live to a ripe old age of 10.
  2. What do Watchman Gobies eat? Answer: They are carnivores and love meaty live foods.
  3. What size tanks do I need for a watchman Goby? Answer: 55 Gallons is a good start but if you want to keep many species of goby in the same tank then you’ll need a much larger aquarium to stop fights over territory breaking out.
  4. How can I tell the difference between male and female Goby? Answer: Females are smaller and often the less aggressive of the two fish.
  5. How much do Diamond Goby cost? Answer: Around $40 in the US and £30 in the UK
  6. What substrate is best for gobies? Answer: Soft fine sand but make sure it’s around 3-4″ deep to allow them to make a hole/burrow to live in.
  7. Do Goby sleep? Answer: Not like humans do, but they do enter into a rest period where they recover.
  8. Do Gobies pair for life? Answer: Yes


Conclusion: Watchman Goby Care Guide

Diamond watchman goby is one of the most colorful and good looking fish there is. It’s well known for being very interesting as well as entertaining, therefore most saltwater tanks have a goby of some sort especially reef tanks or nano aquariums.

This species is among the easiest species of goby to look after, and so you won’t have a hard time keeping them around. Just ensure that your aquarium is of the right size, the water temperature is ok and that you feed them the right kinds of foods. Saltwater shrimps often make good tank mates and often share the same home and work together as a team when it comes to feeding and living in the same space.