Vietnam - Rambo Country for marine aquarists

If you've never been to Vietnam and haven't seen any documentaries about it, you're more likely to associate Vietnam with the Vietnam War and Rambo than with deserts and gorgeous reefs teeming with stony corals.

But it is precisely this unknown Vietnam that arouses curiosity and the explorer in us! But why Vietnam, whose marine fauna displays a mix of Thailand, Malaysia and the Philippines? 

Perhaps because Thailand and Malaysia are overcrowded and divers are already flying to the Philippines. Vietnam is no longer an insider tip, but it’s still quite undiscovered. You can be so isolated in the jungle that you half expect an old soldier to come out of the bush at any moment, not having realised that the war has been over for 35 years! 

We seawater fans like to take in the beautiful temples, the exotic food and the jungle next to the desert parts (near Nha Trang), but always really look forward to having some encounters with the marine life. In Phuket/Thailand, about 90 boats with divers leave in the morning to visit the surrounding reefs. In Nha Trang, about 500 km northeast of Ho Chi Minh City (the former Saigon), 2-3 boats leave for diving in the morning. However, due to offshore islands, they do not run into each other, but try to stay out of the way. Most of the beautiful reefs are scattered around Hon-Tre Island and Hon Mun. This is also where the 11 best diving spots in the whole region are located.

Due to their locations the reefs are extremely varied. Even above the water our experience tells us where we may find strong coral growth and where we can expect to find current-swept rock formations with few corals but lots of fish. As soon as a peak protrudes from the sea at islands, the current increases exponentially there and the underwater fauna changes. Encounters with big fish like mackerels, sharks and barracudas are much more likely there than in sheltered bays where the reefs can grow in peace. Here gentle swimmers like seahorses, boxfish, juvenile batfish or even the beautiful longfins swim around in peace without being displaced hundreds of metres by a current surge and then unable to find their way home.

The (almost) coral-free rocky reefs

Even for coral fans a detour to the (almost) coral-free rocky reefs with washing machine-like currents is worthwhile. Where else can we see about 30 Moorish idols swimming in formation over the rocks? It is also interesting for us to see which corals prefer or avoid these current-exposed places! Soft corals always have the advantage in turbulent water because, as their name suggests, they are soft and can give way. Hard corals have their problems with giving way. They tend to break, which is why the few stony corals in such places tend to be bonsai versions or simply non-existent. In addition, we as humans experience how inelegantly we are at the mercy of the sea. No matter if we are on the chubby side or swim like a streamlined athlete, we are tossed back and forth like a shopping bag in the boot of a car on a fast-winding ride. When this happens I find myself looking enviously at the fat sharks, well-nourished and quite chubby, which can rest completely at ease in the current. They don't have to move a single fin - they just look on with pity! 

Better to quickly head back to a quiet bay and simply enjoy the natural giant aquarium in peace and quiet at shallow depths and without currents. The reefs rise from a depth of 10-20 metres to the water surface and are only limited in their growth by the movement of the waves and contact with the air. This is nice for the snorkellers, who can finally observe the life in the reef next to them, instead of from the helicopter perspective. And it really is varied here!

The diverse life in the reef

But unfortunately the most beautiful, colourful and bizarre organisms we see now are completely unsuitable for aquariums: the sea slugs! Almost every species requires a different food and each food is so specialised that it takes a lot of luck to successfully maintain a sea slug species in the aquarium long term.

Even though anemonefish can now really be found in almost every tropical sea (except the Caribbean), they always cast their spell on us. And even at the hundredth encounter, we can still discover something if we look closely: How many clown fish actually live in an anemone and what is the minimum size of the anemones in which a pair lives? How many generations live together in an anemone? Which other fish are tolerated? How far do the fish move away from their anemone? Do other inhabitants like shrimps or crustaceans live on the anemone, maybe even both at once?

In the aquarium, most butterflyfish species are more of a nuisance than a pleasure, as they constantly pick at our painstakingly cultivated and expensively purchased coral polyps. Vietnam is a butterflyfish paradise! Here you will see over 10 different species in 30 minutes underwater and you can relax and watch as each species eats its preferred coral without it hurting your wallet. It is also worth spending some time observing the dwarf angelfish species (Centropyge): Individuals of the same species do not always eat the same things. Sometimes corals are on the menu and sometimes not - just like in the aquarium. Pygmy angelfish and marine angelfishes are sought-after photo subjects because of their beautiful colours and have driven many a photographer crazy. But if you know their behaviour a little, you know how to catch them: Almost all angelfish swim away first, but they are one hundred percent likely to turn around ONCE to see if their pursuer is still behind them. This is then always the best chance for a nice portrait photo.

The small damselfish, which "only" beginners among marine aquarists buy and often swim unnoticed in the dealer's aquarium, take on a completely different meaning under water. Anyone who watches a shoal of demoiselles above a staghorn coral (Acropora) disappear into it in absolute synchronicity in case of danger, only to have them all emerge from the shelter again shortly afterwards, is so fascinated that they will never again walk carelessly past them in the pet shop. The lightning-like hiding between the coral branches and the appearance like a cloud from the coral is indeed one of the most beautiful occurrences in the reef. There are also really many small damselfish species that are incredibly beautiful in colour. Only some lose their beautiful colour when they get older and become not only ugly but also extremely aggressive! Damselfish are also one of the few fish species that actively attack divers or snorkellers. Their bite marks, however, are rather microscopic, in contrast to the titan triggerfish, which once bit a less attractive hole in the cheek of a fellow diver right before my eyes. Today, this hole is adorned with a thick piercing! Necessity is the mother of invention...

But even if occurances like anemone fish and damselfish always fascinate us, we are also eager to discover something special. Animals that Mr Jones from next door won’t see in the Maldives. No problem, Vietnam can offer that too: 

Ghost pipefish quite often swim in the protection of the spines of diadematidae sea urchins. Since they feel protected there, they stay and can be observed in peace. This is different with puffer and box fish. They bolt and you can only follow them with your eyes before they hide under a table coral. That’s where we usually find them and they’re usually easier to observe in peace in the protection of the coral. Beautifully coloured mantis shrimps are not that rare either. If you do miss them, you can enjoy them in the restaurant aquarium in the evening and later on your plate.

Pipe fish live in crevices and on well-protected reef areas. I was captivated by these animals from a very early age. I have never forgotten the not-seriously-meant statement about the close relationship between seahorses and pipefish: "If you pull a seahorse lengthways, you get a pipefish" - species studies in advanced biology.

If the rarities are not enough for you during the day, you can plunge into the nightlife, which is well worth seeing - underwater, of course! Before me, no one had been diving there at night, and after my night dive, a law was passed that the sea may only be entered at night from the beach and with advance notice. We could never fathom what really prompted this new law. It is a pity, because at night, as is well known, animals appear that are never or very rarely seen during the day. One of the highlights was stump-tailed sepias and an octopus trying to imitate something. I just couldn't figure out what it was supposed to be. By the way, at night, unlike during the day, the sandy bottom is worth it! Many a creature crawls and creeps and burrows on the otherwise mostly boring habitat. 

The following water values were determined on the JBL expedition to Vietnam (at various locations around Hon Mun Island):

Surface water temperature:  28.8-29.6 °C
Conductivity:  50.5-50.8 mS/cm
Density:  1.022-1.023
pH:  7.8-8.2
KH:  6-8 °dKH
Ca:  420-480 mg/l
Mg:  1020-1460 mg/l
O2:  mostly 10 mg/l

If you ever get tired of the beautiful coral reefs, rent a small moped and simply turn off a main road into the jungle. Signposted waterfalls are always worth visiting, because there you will find clear fresh water with one or two surprises swimming around: from snakeheads to barbels to very interesting gobies!

Travel tips:

Most 11 h long-haul flights end in the 8 million-strong city of Ho Chi Minh City (formerly Saigon). Take a day to explore the city and maybe another day for "the mother of water", the 5000 km long Mekong River. You will never get on the same day by plane to your actual destination in central Vietnam, e.g. Nha Trang. This place with 500,000 inhabitants actually offers everything we would like to see. There are hotels between €12,- and €300,-/per night. Most are around 35,- €/night. With a small moped or by taxi, all distances are easily manageable and affordable. German citizens do not need a visa to enter the country. The cost of living is much lower than in Germany and you could easily afford your fill of lobsters every evening. The Vietnamese are a very friendly people and always allow photos to be taken. Long-haul flights with Vietnam Airlines start at €600 and domestic flights, e.g. to Nha Trang, cost an additional €50 each way. Divers pay around €60 for 2 dives and only need to show a basic diving licence such as the Open Water Diver.    

© 16.10.2022
Heiko Blessin
Heiko Blessin
Dipl.-Biologe

Tauchen, Fotografie, Aquaristik, Haie, Motorrad

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