PH Marine fish question?

Question

Ok lost a shark and a vtail grouper this week. My ph has always read low 7.8. All other parameters are 0 except nitrites which are in between 0 and .25 and the nitrates that are most likely .25, but theres a bunch of nitrate absorbers in the filtration systems on the tank. Honestly its just hard to read since you have distinguish shades of yellow. It looks to me as if its 0. My KH test indicates its closer to 200 ppm and im adding kent buffer to stabilize my ph. My main question is whats killing my fish. The shark was stressed for quite some time (theres two of them). Towards the end she was flashing hard on one side with no signs of external parasites. My v-tail just turned up dead hid most of the time ate once may have just been sickly in nature not sure but because they both died so close together Im really curious if the ph could of caused it. If anyone has some ideas on why this is happening other then i have water quality issues please let me know.

All fish in tank are small right now only have a years stay till we get a 300 gallon (75 gallon right now). There is live rock bout 20-30 pounds, 60 pounds fine grain sand, a water circulating pump, a fluval 400 canister pump, a penguin 400 bio wheel filter, a seaclone 100 skimmer, and a uv steralizer that runs at about 45 gallons per hour to kill parasites. Heck I have an anenome alive and well I really dont see how the grouper croaked and not the anenome. My only fear is somethings in the tank that passed off the shark into the grouper and hopefully no where else. Is there anything like this or is the low ph screwing with them. Also my salinity is on the high end 6 i measure via a hydrometer.

Answer 1

In my experience buffers don't work all that well to raise the pH, even if you have an aragonite substrate- crushed coral or shell material in the tank. I used to live where I had the perfect water for marine and cichlid tanks - pH near the mid 8s right out of the tap. Now it's closer to 7, and like you I had a lot of trouble getting above 8 at all. The only thing I found that would raise it and keep it stable was kalkwasser (calcium hydroxide). This comes in powder form and is very caustic, so you need to be careful using it or it will cause a chemical "burn". I mix it with water in a clean plastic bottle. Usually a dosing system (like a hospital IV bag) is used to deliver a constant, slow drip to the tank, but you can add some with a medicine dropper once or twice a day, depending on the size of your tank and how much you need to bring the pH up.

Also, you don't mention your salinity. You should monitor this with a hydrometer, not use the 1/2 cup per gallon directions on most mixes. I have yet to find a salt mix that gives the correct salinity with that amount, plus the salt compacts with time as it absorbs moisturem so the volume won't be consistent. What you want to aim for is a salinity of 1.020-1.026 for fish-only tanks, or 1.024-1.026 for tanks with inverts. The exception would be if you keep wild caught Red Sea fish where they are used to a salinity closer to 1.027. When you mix up new salt, use cold water, so you don't introduce dissolved metals from your hot water tank and pipes (some metals can be toxic in high enough concentrations), and wait till the water is room temperature at least befor measuring/adjusting the salinity because this is temperature dependent. Salinity changes 0.001 for every 10o change in temperature.

Do you use a protein skimmer or live rock in your tank as part of the filtration? If you're getting nitrites, either your tank isn't completely cycled, or you're getting a buildup of organic materials from some source (dead fish, overfeeding, inadequate cleaning). A skimmer will aslo increase the dissolved oxygen, which might also be a contributing factor in the death of the fish if there isn't adequate water movement in the tank (cannister filters do a good job of filtration, but produce little surface movement in the water for oxygen-carbon dioxide exchange).

ADDITION: From your added details, none of the items I mentioned should have affected the fish but not the anemone - except possibly for the dissolved oxygen. If your power had been out overnight for any length of time, and the fish sleeping at the bottom of the tank, it's possible there could have been some oxygen depletion that may have affected the fish, but not an anemone higher up in the water (closer to the surface where there would be better oxygen exchange). That doesn't explain the flashing nor the damaged dorsal you mentioned in an email. It's possible that one of your fish had a parasite and passed it to the others (did you notice any thickening of the slime coat rather than distinct spots on the fish?). It's possible that the fin damage came from the flashing, or you might have introduced a predator (crab, mantis shrimp) with your live rock. If you have the capability, I'd put the remaining shark in a separate tank with just a filter, heater, and hiding spot. If you've got a predator, it will be safer for the shark, if we can identify a parasite, it will be easier to treat him in a smaller tank (and the anemone and other inverts won't be affected by any medications.

Even with a UV sterilizer, it's still possible to have parasites and diseases show up in your tank. If they come attached to the fish, are able to swim well enough to avoid being drawn into the UV, or are too large to be affected by the radiation, the UV won't have any effect.

ALSO: what species of shark and age/size?

Answer 2

this is a tough question, a seahorse really needs to be housed alone is a species only tank, so really unless you plan on getting a second tank, your first fish needs to be a seahorse, however as the person already said a seahorse isn't technically a beginner fish, how do you like that? in truth if you read all you can from good sources, and have nothing else to focus on but your seahorses i think it can be done, ph in a marine tank can require a chemistry degree to fully understand, ph is affected by a number of things including but not limited to CO2 vs O2 saturation, light cycle, buffering capacity in relation to alkalinity dependent on its balance with calcium and magnesium, go all that? all you really need to know is that it should stay bellow 8.5 during the day, and above 7.9 at night, anywhere in that window is acceptable, you don't need to know the rest until it breaks those boundaries