The ocean’s chemistry is really pretty simple: it eats rocks. It supports organisms that, from microcellular up, eat the dissolved rock and eat light of a favored spectrum, which energizes their little cell-parts and makes the eating re-constitute into shells, tissue, skeleton. If conditions go ‘off’ it fosters areas of the food chain that ordinarily are very sparse, and other things start to grow—like cyanobacteria, which lives on sunlight as a sheet of red thick feathery slime, photosynthesizes simple sugars, and gives off oxygen bubbles.
If it weren’t for cyano, earth wouldn’t have an oxygen atmosphere, wouldn’t have recovered after the Permian Extinction, and wouldn’t have green plants—which developed incorporating an element of cyano. It’s part of earth’s balance: the atmosphere goes wonky enough to distort the solar spectrum and you get lots and lots of cyano. Piles of it.
If it happens in your tank, alas, not so good. So you have to keep your lights burning true to the sun’s spectrum…and metal halide bulbs don’t so much burn out as ‘burn down’, or yellower.
Things die, and the ocean dissolves their skeletons and new critters suck it up and build their skeletons. The precise amount of calcium ocean water can dissolve is 2 tsp a gallon, unless the ph is high. Then maybe 2.5. People put white vinegar in their tanks to force a bit more into solution, but you have to supply the calcium in the first place…and what we use is, yes, Mrs. Wages’ Pickling Lime, meant for cucumber pickles. Works like a charm, dumped into the fresh water we add as make-up for evaporation.
A marine tank is surprisingly little care, so long as you keep fresh water slipping in via a float switch (a lot like your toilet tank) and keep the water circulating and a high rate of speed and the calcium in the water sufficient—since no more than 2 tsp WILL dissolve, I don’t even measure: I dump a whole packet in and trust basic chemistry to happen. You have to change out the lights periodically. And there’s a device called a skimmer, which produces bubbles in a chamber and extrudes froth, which is amino acids the system doesn’t want: with that, pure water, a good salt mix you buy—things are remarkably stable and coral grows and fish thrive.
A lot of people get spooked off aquaria at the goldfish level—and the pure answer is—goldfish are a type of fish better off in ponds, not gallon jars. They don’t get enough exercise and eat too much: recipe for bad health; and one gallon doesn’t provide enough oxygen, either: if in the least dirty, the water carries even less oxygen. And tapwater is full of stuff they shouldn’t be breathing, even if you correctly use water conditioner to remove the chloramine. Small wonder goldfish demise. They’re NOT an easy fish in the first place.
The hobby as a whole has marvelous equipment compared to what we used to use. We’ve got one freshwater and one marine tank, the latter of which shouldn’t have been as much trouble as it’s been, except that I got some iffy rock, which has taken months to condition into honest live rock—[meaning it’s got bacteria living all the way through it and it’s soaked out all the phosphate it came in with]—which now serves as a very important biological filter. It’ll be great rock, now. And the coral should start to grow.
This is how the 
tank arrived. 800 lbs. In the street. If it hadn’t been for Mike and Patty Briggs, who drove up from the Tricities (150 miles one way) to help us, and Tim Martin who came straight from work—we’d have been in real trouble. If you’re interested, I’ll show more pix of the tank during setup.
Goldfish are not better off in the ponds of Oregon!
“Mann Lake, a remote but formerly significant home to Lahontan cutthroat trout southeast of Burns, has been poisoned to rid it of unwanted goldfish. … Goldfish became so prevalent they could be seen from the air, described by at least one pilot as “like a golden halo” around the lakeshore. Few Lahontans remained as the goldfish ate most of the food. … Oregon Department of Fish and Wildlife officials said preliminary results suggest approximately 170,000 goldfish died from the rotenone treatment.”
That’s only one of the times it was necessary.
Definitely: as with our koi—they are bred to grow rapidly and eat most anything—including other fish. They were originally bred as village food fish, and are survivors—the faster and the smarter avoided the net. Dumping ANY aquarium fish into a natural pond, lake, river or ocean is not a good idea. Witness the proliferation of lionfish in the Caribbean, or of caulerpa algae in the Med. Disasters.
My last attempt at a tank was a 20-gallon freshwater. The pH of the local water, even after sitting and gassing out for several days, was too low, so I added the correct amount of baking soda to bring it to a comfortable range. I thought all was well, but when I checked it a day or two later, it was acidic again. This kept happening, and I finally gave up and gave the whole setup away.
I have since been told that the baking-soda treatment is only temporary, that the effects “evaporate” or something. Had I known that at the time, I would have found a better solution and would likely still have the tank.
Ph can change due to your house heating, due to the presence of certain minerals in the tank’s rock, etc, and due to the lack of mineral in the water itself. Buffered additives are more efficient than baking soda—more stable. I haven’t kept up with what’s available in that department for fresh water, since ours is pretty ok, but a marine tank doesn’t even try to watch ph, which is typically all over the map (because of marine chemistry) during a given day. If you have a calcium of 420, an alkalinity of 8.3 and a magnesium level of 1250+ your ph will be somewhere around 7.9 to 8.3, pretty steady (absent a wonky furnace in your basement, etc), nor will the numbers change (given a continual availability of powdered calcium (which corals use hand over fist) to be dissolved as the water ‘needs’ it—until the magnesium level (which corals use very, very slowly) falls below 1200. Then all the numbers will start to crash. It’s an intricate bit of chemical relationship, but far from hard to maintain. In some measure, I consider marine tanks, once established, easier to keep than freshwater. We have more gear—but when it runs, it runs.
The simple version is, for a marine tank, run the 3 tests, supplement your deficiencies until you hit those numbers, then test the mg once a week until you see it fall…give it more mg, and just keep it up until, somewhen several months on, you need to reset the levels…usually because you weren’t paying attention!
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