Re:male seahorses died

Pete Giwojna

Dear Peg:

Rats! I’m very sorry to hear about the problems that cropped up with your seahorse tank and eventually led to the death of Trigger and Milo — all my condolences on your losses!

It’s clear from your description of events that your seahorse tank experienced a vegetative event — a massive die off of a colony of Caulerpa, which happens very quickly and can be very hard on the aquarium inhabitants. A sudden die off of a bed of Caulerpa due to stress or sexual reproduction can cause a small closed-system aquarium to turn milky white in a matter of moments. This can be harmful because toxins may be released by the Caulerpa in the die off and the resulting decay of a considerable quantity of vegetable matter can degrade the water quality and reduce the level of dissolved oxygen in the tank due to a bacterial bloom. In severe cases, this combination of events can stress the other aquarium inhabitants or even wipe out the entire tank.

I suspect that something along those lines is what overwhelmed Trigger and Milo, Peg. The toxins released by the Caulerpa and the dangerous drop in the dissolved oxygen levels would not have been detectable on the standard aquarium test kits that measure ammonia, nitrite, and nitrate.

Your instincts were very good during this crisis, Peg. The proper response to such a vegetative event is to install chemical filtration media to remove any toxins that may have been released and to perform a series of water changes immediately until the water clears. Extra airstones anchored just beneath the surface to provide extra surface agitation will promote better oxygenation and gas exchange at the air/water interface, helping to restore the oxygen levels more quickly.

The chemical filtration media I prefer for such a problem are a good brand of activated carbon for adsorption and absorption used in conjunction with a brand new Polyfilter pad to provide chemisorption of any toxins. The Chemipure was not a bad choice, although not as efficient as a Polyfilter pad or new activated carbon for this type of emergency, and I don’t believe the Chemipure had anything to do with the loss of your males (I have used Chemi-Pure many times on various marine aquariums, including seahorse tanks and it has always been very beneficial).

Either some toxic substance or the drop in the dissolved oxygen levels, or both, stressed Trigger
to the point that he fell victim to an optimistic bacterial infection, which caused the sloughing of his skin, and also knocked Milo for a loop. I am not sure why this event hit the males so hard, yet left your females relatively unaffected; apparently a difference in their physiology, metabolism, or hormones made the stallions more sensitive to the harmful effects…

But for whatever reason, Venus and Sunny seem to have escaped unscathed, and if they are doing fine at this point, I’m confident that they will continue to thrive now that the crisis has passed. However, it would be prudent to increase the aeration or to add an extra airstone or two to your main tank at least for a while in order to assure that the dissolved oxygen levels are back up to normal.

It was very good thinking to treat Milo and Trigger with a quick dip in a 3% hydrogen peroxide solution followed by a dip in concentrated methylene blue. Those are the perfect first aid measures to take whatever hypoxia or a lack of oxygen is suspected, or an unknown toxin is at work. The 3% hydrogen peroxide increases the dissolved oxygen levels in the solution, helping the seahorses to breathe even as it disinfects open wounds or ulcers from a bacterial infection. Methylene blue can reverse nitrite poisoning, ammonia toxicity, and cyanide poisoning and converts harmful methhemoglobin back to the normal hemoglobin in the fish’s red blood cells, helping them to breed normally again. Unfortunately, evidently Trigger and Milo were simply too far gone for these first aid measures to save them…

But Venus and Sunny have weathered the storm and I think they are probably out of danger at this point. Try to increase the aeration in your main tank and consider adding some fresh activated carbon and/or a new Polyfilter pad to your aquarium filter as an added precaution.

If you’re growing Caulerpa in your aquarium, Peg, it can normally be prevented from going sexual and dying of simply by repeatedly pruning are aggressively thinning out the colony. This is accomplished by regularly plucking out excess fronds of the fast-growing Caulerpa; when you subsequently you remove the excess Caulerpa you’ve plucked out of the main colony, you’re exporting phosphates, nitrates and other nutrients from the tank, thereby helping to maintain good water quality, and pruning the runners helps keep it from going sexual.

When pruning or trimming back macroalgae, take care not to actually cut it. Remember, you’re not pruning hedges or trimming trees — the idea is to carefully pull up and remove continuous, unbroken fronds. Simply thin out the colony of excess strands, gently plucking up convenient fronds that can be readily removed intact. A little breakage is fine, but cutting or breaking too many strands will result in leaching undesirable substances into the aquarium water as the Caulerpa’s lifeblood drains away. Too much cutting or breaking can thus sap the colony’s strength and cause die offs or trigger the dreaded vegetative events that judicious pruning otherwise prevents.

If you’re concerned about your ability to maintain and control of Caulerpa properly, Peg, just use a different forms of macroalgae that grows less rapidly instead and you can get the same sort of benefits at relatively little risk. In that case, some of the other macroalge you may wish to consider are Gracilaria, Ulva, Chaetomorpha, and Chlorodesmis. Hawaiian Ogo (Gracilaria sp.) are bushy red-to-brown macros that do well under low light levels. Sea Lettuce (Ulva sp.) are deep green sheets of algae that do best under a little stronger lighting. Maiden’s Hair (Chlorodesmis sp.) are bright green tufts or clumps of very fine-bladed algal mats to grow attached to small rocks. All of these types of macroalgae are much less prolific and slower growing than Caulerpa. However, like all macroalgae, they should still be harvested periodically in order to export the excess nutrients they have consumed.

Aside from red and brown Gracilaria and the bright green Ulva and Maiden’s Hair, some seahorse keepers also like the Chaetomorpha turf algae. It is popular because it is slow growing and doesn’t require the kind of pruning that Caulerpa needs, and because it it comes loaded with microfauna: miniature feather dusters, copepods and amphipods, tiny snails and micro stars. Sounds like another interesting marine plant that can add some extra variety to a lush bed of macroalgae.

Some macroalgae are rootless and do not anchor in place. This is true of the Chaetomorpha turf algae or spaghetti algae, for instance. It grows in tangled clumps that look like nothing more than the colorful green Easter grass we use in our Easter baskets as bedding for the jellybeans, marshmallow chicks, and chocolate bunnies. Chaetomorpha is therefore not very aesthetic looking in your main tank, but you can’t beat it for use in refugia or algal filters because hordes of copepods, amphipods, and other microfauna love to shelter, feed, and breed in the tangled masses of the spaghetti algae. (The chaeto was a great choice for your sump/refugium, Peg.)

If you copy the following URL and paste it in your Web browser, it will take you to an excellent article by Anthony Calfo titled "Best Plants and Algae for Refugia — Part II "Vegetable Filters" that will explain the benefits provided by various species of macroalgae in a refugium in more detail, Peg, including the dreaded vegetative events that can happen with the fast-growing Caulerpa:

In short, Peg, I think you lost your males to a fluke event when your bed of Caulerpa went sexual, and now you know how such a problem can be prevented in the future, so you will hopefully never again have to deal with this phenomenon.

Best of luck getting your seahorse tank back to normal again, Peg. Here’s hoping Sunny and Venus live long and prosper despite the loss of their mates…

Pete Giwojna

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