Sick tangs and tank dimensions

Question
Jennifer, I added a Powder Blue Tang in my tank last Thursday and yesterday, it died along with my Sailfin Tang.  it is horrible. I can't believe this.  I tested my water and the water tests normal. no nitrates,no nitrites, no Ammonia, pH at 8.3 and Alkalinity normal.  what could have happened? the tank is a 75G.  2 teeny perc clowns, Flame Angel, Bicolor Dottyback, Yellowtail Damsel, Yellow Tang, 2 Crocea Clams, Clean up Crew, Zenia, Hairy Mushrooms, Zoos, Colt Coral. oh. Mandarin Goby.  Not sure what happened. I do weekly 10% water changes. going to install a refugium this week. got some amphipods and copepods in there ,too.
one other questions.  i want to get bigger tank. 48"by 24" by 31" or 48" by 24" by 35".  that height is nice but how does one do aquascaping when the tank is that high? tongs are not that coordinated. do you think the extra 4 inch height is worth it? lighting getting through the water? thanks. Vu

Answer
HI Vu. Sorry to hear about the loss of your fish. Did you happen to notice any bullying going on between the tangs? No matter how many times I say this most people don't know that tangs should not be housed in the same tank together. The rule with tangs is one per 48 inches of tank length. Some tangs will get along for a little while but eventually their territorial nature will take over and one will become the dominant tang bullying and picking on the others and not letting the subordinate tangs feed or have the freedom and swimming space that they so require. Tangs are territorial over feeding space and will fight with one another as to not let each other feed in their space. These feeding grounds that they require are vast and in a tank environment you can bet the entire tank belongs to one fish! I have personally seen tangs pick other tangs to death! There is also the problems associated with stress from being in an enclosure with one of your enemies. Stress leads to a lower immune system which in turn leads to poor appetite, infections and disease. Yellow tangs can be very aggressive and I find it very interesting that the only fish that died were two of your three tangs...? Now since you tested your water you can rule out a problem with that as the cause. If you saw no signs of a parasitic infection or any other kind of infection then you can almost rule out disease which leaves you with severe stress from bullying or starvation from being stressed out and bullied. Another bit of info for you; Yellow tangs get up to 8 inches full grown; sailfin tangs get 10-12 inches full grown and powder blue tangs get 10-12 inches full grown. That is about 30 inches of fish in your 75 gallon tank with just tangs alone! Generally you only want to keep 1 inch of fish per 3-5 gallons.(in a 75 gallon tank this means about 15-25 inches of fish maximum) In total with all the fish you have at full grown size you would have had around 1.5 inches of fish per gallon. Do you see what I am getting at? Now this isn't why your fish died but it would have been the cause eventually. Overstocking your tank is never a good idea and can lead to many, many problems in the future for you tank. Corals are very intolerant to high levels of fish waste and reef tanks should be kept at the lower end of the stocking levels.

As for the size of the two tanks you listed go for the shorter one! Height in any fish tank is basically just a waste of space. Its length that matters as far as swimming space for your fish goes. Also in a taller tank less light will penetrate and you may have to have stronger lights for a taller tank. You should opt for a longer tank over a taller tank and if length is an issue save some money by buying the same length tank with less gallons due to it being shorter.