I had the distinct privilege of hearing Gerald Heslinga of Indo-Pacific Sea Farms discuss Tridacna clam aquaculture while at NextWave. Tridacnids are of particular interest to me, as I find them to be both gorgeous and individually unique, not to mention I’ve owned and gawked at a countless number of them throughout the years, so I found the presentation to be quite entertaining. Continuing on with the clam discussion from this past weekend, I’ve stumbled across a great video from Gerald and Indo-Pacific Sea Farms.

The video above focuses on four species of giant clam, T. crocea, T. maxima, T. derasa, and Hippopus hippopus since each can be found in the home aquarium and each represents a different type of morphology. The crocea and maxima clams are grouped together because they both have a wide byssal opening. This opening is located on the ventral side, or bottom, of the clam and is the area where the foot and byssal threads emerge to keep the clam attached to hard substrate. Because the area is so large, it is the clam’s most vulnerable spot. In the wild, these two species solve this problem by burrowing into the rocks, but in the aquarium their ability to achieve this protection depends entirely on where the hobbyist places them. A crocea or maxima clam in the sandbed is particularly exposed, especially since that’s where a majority of pests and predators occur.

The next two clams on the list are T. derasa and H. hippopus. They differ from the maxima and crocea clams in that they have a tiny, if almost non-existent bysall opening. As juveniles, these openings do exist to a greater extent, but as the clams age the opening closes. In the wild, derasa and hippopus clams live on sandy substrates and can grow quite large. For these reasons, neither of these two clams rely much on their byssus, and both are less prone to parasites and predators getting access to soft tissue via the bottom of the clam. In addition to a tiny byssal opening, H. hippopus has a thick shell and a shell hinge that comes together almost like a zipper. Because of this, hippopus clams are the “most predator- and parasite-resistant of the giant clams in mariculture operations and probably in aquariums as well”.

The take-home message to all of this is placing clams on the correct substrate is crucial to their long-term health and stability. Clams are very hardy and easy to care for, however predators and pests can find their way into your aquarium along with your clam.

The pictures from our friend in Kwajalein keep rolling in. As he explores the islands and gets more comfortable with his surroundings, new areas are getting explored. This update is focused on one of my favorite aquarium invertebrates, Tridacna clams. Both T. crocea and T. maxima clams can be seen in tidepools. The clams are burrowed into the substrate and some are even exposed at low tide. The clams of course are used to being exposed at low tides, so this isn’t an issue so long as the tide returns within a few hours. To stay wet, the clams close up and keep as much seawater in their shell and tissues.

I stumbled across this interesting video over on the Reef2Reef Forums the other day. It’s an older video, though recently uploaded, that shows how Tridacnid clams are farmed. This Palau facility uses the nearby ocean as a major area for growing the broodstock clams, with the land-based portion reserved for breeding, juvenile grow out, and larvae rearing.

The most interesting portion of the video demonstrated how the facility’s staff induced clam spawning events. They would pick a mature clam, cut out its gonads (of course killing that individual), and squeeze the gonads near the incurrent siphons of sexual mature clams. This action would release horomones into the water, causing the clams to almost instantly release a cloud of sperm. Being hermaphroditic, the clams would later release eggs as well. The clams releasing eggs would be removed from the tank and placed into individual containers, where egg capture would be much easier. The fertilized eggs would then be loosely counted and placed into a large holding tank where the larvae would mature. The larvae would settle onto the bottom of the tank, where they would acquire Zooxanthellae and continue developing. After approximately 12 months, the clams would be available for market, which consists of the aquarium trade, replenishing local reefs, and even the Japanese sushi market to name a few.

Tridacna crocea among Zoanthids

Here is a gorgeous Tridacna crocea clam living among Zoanthid polyps.

A Dolphin Fountain at the Maui Ocean Center

In June of 2007 I had the privilege of going to Hawaii for my honeymoon. Our primary destination was Maui, but we got to spend a day in Oahu. While in Hawaii, my understanding new wife let us go to see two public aquariums: the Maui Ocean Center and the world renown Waikiki Aquarium.

The Maui Ocean Center was an accidental find. While exploring the island, my wife and I drove right past it and I nearly locked up the brakes. It was closed when we initially drove past, but we quickly made plans to return. As you enter the Maui Ocean Center, you

Here I am at the entrance to Waikiki Aquarium

immediately see an outdoor lagoon-style display with a waterfalls and tons of large tangs and triggerfish swimming around. After gawking at the outdoor display and identifying all the fish trying to impress my wife, we made our way inside. Upon entering, the first thing I noticed was that every single tank had real corals in them. This was a huge difference from the public aquariums in Texas. For example, the Houston Zoo, Moody Gardens, and Aquarium restaurant all had fake corals somewhere in their displays…but not here.

We continued through the small facility looking at the variety of fish and corals present. They had a lot of native Hawaiian species, as well as

Waikiki Aquarium Outdoor Lagoon

some from other parts of the world. Additionally, they had an outdoor touch tank which I didn’t pay too much attention to as I used to work at Moody Gardens and people abused those poor animals regularly. Overall, the Maui Ocean Center was nice, but nowhere near as impressive as the Waikiki Aquarium.

On our last day in Hawaii, my wife and I went to the Waikiki Zoo (sort of a drag as most zoos seem to be nowdays) and the Waikiki Aquarium. The Waikiki Aquarium blew my mind. When you walk in, you immediately see some gigantic reef tanks. These were stunning. Each tank was full of giant clams, some of which were several feet long. They also had some awesome anemone tanks that were completely packed in with

Waikiki Aquarium Outdoor Lagoon

gigantic anemones hosting various clownfish. I was like a kid in a candy store…pointing out what I had, what I wanted, and drooling all over myself.

Moving through their facility, I saw Amazon setups, octopus tanks, some neat looking jellyfish, and a tank full of huge fish, including a six foot long goliath grooper. And just as you exit the door and think your trip through paradise is over with, you see the outdoor displays. The first tank is a massive outdoor coral tank full of large tangs and butterfly fish. At the opposite end of this setup is a biologist displaying a few things you could touch. I

Huge Tridacna gigas clam

made my way over to see what he had, and little did he know I myself was a biologist. He tried to talk to me about saltwater hermit crabs and urchins, but quickly stopped talking when I told him I was also a marine biologist and had been in the saltwater aquarium hobby for a while. It was a little odd, but he didn’t want to chat with me any longer I guess.

Anyways, I moved on and saw the outdoor sea lion display, which has never interested me all that much, and I continued forth. Following a small brick path I eventually made my way to the most beautiful site of all…the outdoor rimless clam display tank next to a large SPS dominated display tank. I saw them and my jaw dropped.

Outdoor Display Aquarium with Tridacna Clams

The SPS tank had huge, gorgeous corals in it. The fish in the tank were limited, but they did have a black longnose tang (Zebrasoma rostratum) which is quite expensive and uncommon. The clam tank was a show stopper. There had to be almost 50 clams in it, ranging from small Tridacna crocea clams to large (and super rare) blue T. squamosa clams, of which there was at least five individuals. For all of you clam lovers, the blue T. squamosa clam can fetch over $500 for a decent sized individual. After drooling at the clam tank, my wife forced me to move on, ending our visit to the Waikiki Aquarium.

If you ever get the chance to visit Hawaii, you have to go to the Waikiki Aquarium at the very least. If you stay on Maui, the ocean center is a nice, short stop, but nothing to be disappointed about if you don’t make it there.

Below is a massive collection of photos from our trip. Click on each one to enlarge them.

Tridacna crocea clam among corals

In the home aquarium, T. crocea clams need to be provided intense lighting from metal halides or T5HO, and need to be placed up high on the rocky structures. Also take care not to put the clam in direct flow from powerheads. Being in a strong, unidirectional flow can cause the clam to close and remain shut, which would prevent the clam from collecting enough light for the symbiotic algae. If the clam cannot collect enough light, it will starve and die.

Other things to consider when picking out a spot for your clam are coral neighbors and the ability of the clam to move on its own. Clams are protected by a thick calcium carbonate shell. However, they do have a large fleshy mantle that can be irritated. Reef inhabitants are always competing for light and a nearby coral can easily sting a clam. The irritation would cause the clam to remain closed during the day and could stress the clam out tremendously. But sometimes a clam can solve the problem of nasty neighbors on its own. They can move about on sand or rocks by using their foot to push them along. Clams move slowly, but only a few inches may be required in order to find a suitable location.

Tridacna crocea clam

Clams are fairly easy animals to keep, but are not recommended for the novice aquarist. Research about proper husbandry is a must and specific types of equipment are required. They are beautiful additions to any aquarium and will certainly attract the interest of guests looking at your tank.