Okay, now that we know your shark will outgrow your tank, let's deal with the now. Please do not add any more fish to your tank until it's completely cycled. You will probably lose your angelfish, but let's try and not let that happen. You definately need tests for ammonia, nitrite, nitrate right now, so you can monitor your parameters and do water changes when needed to keep your fish alive. My recommendation is to get a master test kit from Aquarium Pharmaceuticals. They usually cost about $15.00 online, and if you copy the add on the PetSmart website, they should honor their lower online price at your local store. Locally, they usually sell for around $30.00, so that's quite a savings! The reason I recommend this master test kit is because it's accurate, it has all the tests you need to start off with, and it's relatively inexpensive as far as test kits go. Make sure the master test kit you get contains the nitrate test. There are 2 AP master test kits, so get the one with the nitrate test. Test strips are a little easier to use, but are known for their inaccurate readings, and are more expensive to use than the drops.
As far as the shark goes, you have 2 options. You can either try and trade him back to the store for a different fish more compatible for your tank, or plan on getting bigger tanks, and possibly donating him to an aquarium that has a tank big enough to house these adult fish. They are beautiful, and you are not the only one who has one in a tank at home. Pacus are another fish that should not be sold to hobbyists because of their huge adult size. WalMart sells them by the thousands. Anything for a buck.
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