Can I keep Tetra / Goldfish / Black moor / Koi in same tank?
No. Tetras are tropical fish. Goldfish/Black Moor (a fancy Goldfish)/Koi are all large coldwater fish. The larger fish would eat the smaller fish and that's only the tip of the iceberg in the long list of why they're not compatible! In the 40g, I would recommend the tropical set up with the Tetras - no Goldfish/Koi at all. Common/Comet Goldfish should not be mixed with fancies like the Black Moor anyway, they can cause the more delicate fancies fatal injuries and grow twice the size. In a 40g you can just about fit 2 fancies or one Comet (temporarily). Comets get 10"-12" excluding fins. The Koi however is completely out of the question as they get between 2-3 FEET long and need a minimum of a 900-1000 gallon pond for one or a pair. They are STRICTLY pond fish, they are not suitable for narrow tanks at all.
How often and how much should I feed my Black Skirt Tetras?
You should feed them 1-2 times a day. But only a little pinch. 4 BST in a 5 gallon is quiet cramped. I recommend upgrading to a 10 gallon. You don't even need to buy a new one, there are CHEAP 10 gallon fish tanks on craigslist that all you need to do is clean it and move your tank + stuff over to it.
Can my 4 black skirt tetras live with 7 goldfish in a 40 gallon tank?
that isn't such a good thing to do goldfish need cold water ant tetras need worm sorry
Can black skirt tetra fish eat gold fish food?
If it says "Goldfish" on the package then, obviously it's not meant for a Black Skirt Tetra to eat. However, if it's just for 1 night or something like that it will be best to just not feed the fish at all for that night until you get Tropical fish flakes. Now, if you can't get the tropical flakes for a week, then feed the tetra the Goldfish flakes, but obviously if it takes you a week to get fish food, you shouldn't own any fish.
Would a black skirt tetra, a neon tetra, a platy, and a glofish go good in a tank together? Tank:44galons.HELP?
I have a tropical tank and have all of the fish that you discribed, assuming of course you did mean glofish (the danios with jellyfish color) and not goldfish. They are doing fine do make sure that tetra and glofish have friends as they are schooling fish (the glofish are happy with danios) The rule of thumb that I was taught was a gallon of water for every inch of fish, use the adult size of the fish.
Can I keep Black widow tetra with angelfish?
Its best not too. Angel fish dont like anything that is potentially prettier than them so they will fight to the death. I would advise against it
If I want to keep 2-4 goldfish, what is the ideal setup for the fish without being overly expensive or massive?
I have to respectfully disagree with Ben here. Asking employees of a fish store is not a good idea in general unless you already know enough about fishkeeping that you can affirm that the staff are honest and knowledgable. Often they are not and give bad advice because they simply don't know better or want to sell you stuff. Instead, look online for information, especially on online forums dedicated to keeping goldfish or fish in general.That being said, goldfish are not necessarily good beginner fish as they require large tanks (20 gallons MINIMUM for one, add 10 gallons for every other fish). They also will grow quickly and to large sizes, so be cautious of that. I believe comets can get to a foot long.Tetras OR bettas are easier, smaller fish that would be better for a beginner. Lemon tetras, black skirt tetras, and others are good. Just be sure to do plenty of research on the fish you want and the method of cycling a tank first. This is a great guide:Guide to Starting a Freshwater Aquarium Joining an online forum like that one will give you a wealth of information and people who are willing to answer your questions.
How many Black skirt tetra's can go in a 5 gallon tank?
Hey nice pick of fish i see. One thing you must know is that skirt tetras are very slow fish and can be very stressed out by other aggressive fish. Thats why its good t stick with its own kind. Whenever you see it moving too fast unless a male is chasing a female they are entering into a state of stress. Stress can be pertained to its size of tank. Now the size of tank depends on if its a baby skirt tetra or an adult tetra. This my little key i used for a long time every adult inch to inch and a half needs at least 1 gallon to stay in any bigger needs 2 gallons and up. A baby fish may need just1/2 of a gallon. So i'd say only 5 adults can fit in a 5 gallon and 10 babies can fit in. Do the math and you can mix and match. Hope this helps
Gold fish and tetra neons?
While neons are labeled tropical fish and goldfish are labveled coldwater fish, that's a serious problem for most fishkeepers to over come. In fact, neons will do well in a general range from about 72F to 85F or higher. GOldfish do best around 68-75F but can tolerate temperatures far above and below that range. As you can see, even those fairly tight ranges over lap. Keep the tank in that over lap range and both fish are happy. The entire "coldwater" vs" tropical" mess is so poorly understood that it's a shame and the problems it causes most aquarium keepers isa real shame. In regards to temp, your fine, go ahead and keep them. The gold fish may or may not eat the ghost shrimp, it's a real toss up. That depends greatly on your specific goldfish. MM