WaterNotes

20: Eight months

January 21, 2006 on 1:58 am | In aquaria |

Well, I’ve finally had a major problem with the seagrass tank. I wasnt sure when, if ever, it would come to this, but I was mentally prepared for it to happen. What follows, dear readers, is the cardinal argument for why a dedicated advanced aquarist (like you and I) should never go on vacation. (!!)

Following a three week hiatus from my tank, during which time my caretaker dutifully dosed nitrogen, topped off with freshwater, fed the jawfish and made sure the lights were working as well as the pumps… my tank was seized by dinoflagellates. I confirmed their ID under the microscope, and was rather upset that tiny microbes were bringing down my seagrass jungle dreams.

While I did not lose any animals (neither snail nor shrimp nor fish) the focus plant of this aquarium, and the species I am most attached too, took a very hard hit. The stargrass population in this tank is now about 20% of its previous population size, and the remaining colonies are in sad shape. Typically when ‘fragging’ stargrass for sending to other aquarists I would snip out a colony of eight plants or so on a single rhizome. This tends to leave enough rhizome tissue and leaf tissue to ensure survival of the plants in the new home, even if they do not take transplant particularly well. What I have in my tank are six colonies of 1-3 plants on single rhizomes. Half the ’suggested’ colony size. They are doing dismally, and I am very worried I may lose the species entirely if my propagation tanks also fail.

I tried several tactics to get rid of the dinoflagellates, first following the no water change philosophy enployed by reefers. This included variations of limiting the photoperiod, increasing water flow, decreasing nutrient dosing and other such things. None of this visibly helped the situation. This early lack of control may have doomed the stargrass in fact. Eventually I tried carbon and heavy skimming. (Skimming! On this tank! That should tell you how hard hit the system was.) All to no avail.

Finally I went back to my instincts and decided that, for a plant heavy tank, a nutrient imbalance must be at work to fuel a microalgae plague. In reefs excessive silicates seem to help fuel a dinoflagellate bloom. Yet, I always use tap water, and I know that the silicate levels did not change greatly from before and after vacation. So the trigger for my blooms are unknown. At least I have a cure: heavy frequent water changes of 30% per day with well aerated, RO/DI pristine water. Good attention to nutrient levels and heavy skimming to boot. All these things together saved the tank. I have not seen dinoflagellates come back yet, at one and a half weeks out from starting the water changes.

Now, it seems strange that such different tactics work in a saltwater system when comparing marine planted to reef. In fact, the systems are so diverse I’m not sure I should be paying attention to many, or any, of the rules setup for reef aquaria. Unfortunately, this does mean I’m very much out on my own in this area. It seems that, in plant and macro dominated aquaria, imbalances are corrected by ‘resetting’ the tank.. a concept out of freshwater planted aquaria and Tom Barr’s Estimative Index of nutrient dosing. Once a nutrient gets out of profile for good controlled growth with limited microalgae, its time to reset the tank with large water changes to bring all the parameters back in profile. Then continue dosing as normal.

Whatever the real mechanism going on here, it worked, and I’m thankful. Lets all hope that the stargrass continues will quickly fill back into all its old places. Oddly enough, none of the other plants, Halymenia or Caulerpa, showed any negative response to the dinoflagellates.

There are other theories to explain the disappearance of the stargrass of course, beyond the dinoflagellate menace. Besides being smothered or poisoned by a toxic bloom they may have simply not liked the environment and died back. Additionally, though I doubt it, the hormone injections may have caused an unforseen reaction in stargrass that could signal plant or root senescence (see here). Also, though I freshwater dipped the heck out of it, the LR nub that held some Chondria from a local reefer may have had some sort of worm, pod or other grazer that likes stargrass. Though I dont see any evidence of grazers on the grass its possible. Heck, anything’s possible, and that’s the trouble.

In other news the Halymenia has done remarkably well, more than doubling in size for boththe main and peripheral colonies. Shoal grass did very well through all the dinoflagellate blooms and other nonsense and is throwing new plant daily. The plant are produced aerially, in a segmented fashion as the rhizome elongates into the water column. Eventually leaves emerge and then roots. I then push the rhizome into the sand so the roots can get a good hold, about 1/2″ down into the substrate. All the ones I’ve done this way have continued to propagate and are doing well. Its surprising to see them throw new plants into the water column actually, I was expecting these to be produced underground. For those that remember freshwater plants, they remind me of dwarf chain swords, which throw new plants into the water column, as opposed to Sagittaria subulata which usually propagates underground via runners. Very interesting. I’d guess I have about twenty new plants since the last update, along with the extra plants to the right side now. So, well on the way back to a super dense jungle.

Pics of the tank:

See how much the Halymenia has grown?

Halymenia frond close up, see the spikes? New frond developing off the main.

Segments showing new plant reproduction in shoal grass.

Halophila Flowers

While the stargrass tragedy unfolded I found myself removing large sections of dead and dying grass tissue from the tank. In one of these, sigh.. many, handfuls was contained a queer looking dull red bulb shaped structure at the center of a leafset. Over the next twenty four hours this structure popped open to expose a gelatinous inner layer with three small 1mm dark ovoid structures contained within the translucent gelatin. The gelatin itself was not sticky or tacky, but it was not hard either. In the ensuing time period this gelatin has dissolved, revealing the three ovoid structures only.

In the beginning I thought I was looking at the fruit, or seed bearing structure, of stargrass. I am not very sure what this is exactly anymore. If its the fruit the three ovoids may be seeds. This would indicate that I had somehow missed the actual flower stage of the Halophila. However, I’m not very sure it is in fact the fruiting body of the plant.

After discussing with wonderfully helpful seagrass biologists from James Cook University in Australia, we have ID’d this structure to be the male flower of star grass. Pollen is released into the water, as star grass is water pollinated, when the red bud like structure pops open. One of the scientists thought that the structure itself was somewhat abnormal, which could be attributed to GA or other hormone interactions.

This also means, unfortunately, that my earliest guesses for male flowers, those seen immediately below, are actually female flowers. In mature flowers that have been pollinated the green spike structure swells with small 0.5mm spherical off white colored seeds which eventually breaks off. Sadly I have no female flowers to speak of in the tank, so there are none to be pollinated by the single male flower that resulted from this mess. But, at least there was a silver lining to part of this overall situation. And, of course, we’re still learning here, so its good for the seagrass community in the hobby as well.

Female flowers in red boxes.