With the first tank we started it with the tetras because the guy at the fish store said they were hardy and would help cycle our tank. we waited 3 weeks before getting other fish. You are right about the shops giving false info! I only bought the knife fish because the lady told me they only got 7 inches and were not aggressive. I just have a feeling the deaths have to do with the tank swap or maybe the change in substrate or both. My husband bought the green tetras and that dojo loach without telling me first or I would have told him we should wait and see how the new tank fairs. Before the tank/substrate change all my fish were totally fine. I did buy the liquid test and am going to use them from now on. My filter is a 40 gallon tetra whisper ex. I did use as much water as I could from the old tank in hopes that it would help the new tank water. So do you think I should get some of that bacteria additive so that mt tank isn't so new?
Boy did she lie to you. Ghosts can be semi aggressive but not always. I own a BGK and it hangs in it's tube most of the day and doesn't bother anything. It's more of, if it can fit in my mouth it must be food type of aggression. He is very timid but will come out when he sees me for food and even eat from my hand. When other fish enter his tube he either swims out or completely ignores them which shows me he isn't really territorial with the other fish. They also can grow to be very big. Upwards of 20" big but typically only to about 12" or so in captivity. They really need at least 75 gals but the bigger the better.
The change in substrate could of caused a drastic change in PH from what they were accustomed to which isn't very good. Having a high or low PH, although some fish flourish better in certain ranges, isn't nearly as important as maintaining a PH. People who have a naturally high or low PH like to try to fight with it to get it into a certain range, but end up doing more damage then good. As long as it isn't really high or really low you should just work with what you have. Most fish can adapt to a lower or higher PH than what is recommended. Although, it isn't ideal for that specific fish, according to their natural habitat, it shouldn't cause that much of an issue. The jump from 6.2 to 7.6 is a pretty drastic swing. I've never been a fan of PH boosting chemicals for just this reason. Other slower changing methods are better/safer in my opinion(crushed coral, egg shells, etc.). The drastic changes in the PH can add stress to the fish resulting in disease and/or death. So that could of been part of the problem.
I never recommend those bacteria additives that "cycle" tanks. Although, they can help correct an issue at the time, many times they just delay a proper cycling because most don't contain the proper bacteria that will eventually inhabit the tank in the first place. They are a business and what's best for business is to keep you purchasing thier product. Most issues can be corrected with partial water changes during the cycling process. If you still have your other tank up and running with fish, there should still be beneficial bacteria in there you can use to jumpstart the cycling process. Unfortunately, the water contains very little bacteria compared to the decorations, plants, gravel, etc. What you can do is take some of the gravel out of the tank and put it into a brand new, never used, stocking. Just rinse out the stocking very well before using. Tie off the top and place it into your new tank. Bacteria should be present in the old gravel that should feed on the ammonia and nitrite. In a few days they should reproduce enough to accelerate the cycling process and cover the entire tank with beneficial bacteria. This method can shorten the cycling time down to as little as a week instead of 3-6 weeks. Also, you could use, if your not already, the filter media from the other tank. Just put that behind the filter so that when the water sucks up into the filter it passes through the old media first then through the new media. This will help spread the bacteria to the new media while at the same time converting the ammonia into nitrite then nitrate. This all depends on whether the other tank has been still running. If you already drained and removed everything from the old tank, the bacteria is most likely already dead and you'll just need to wait for the cycling process to do it's thing or if you know somebody with a tank ask them for some gravel. I usually avoid this due to the fact you might, unknowingly, introduce something to your tank but it is an option and a lot of people do it.
Just be diligent with checking the levels daily and do a 10-15% water change if anything starts to get high. Once you start to read some nitrates, and have 0 ammonia and nitrite, your tank should be good to go. At this point slowly add fish. 1-2 here and there until fully stocked. If you add a bunch of fish at once, you'll shock the bio filter causing another mini cycle that could last weeks, depending on the number of fish added. This could result in death or disease in the tank. By adding fish slowly you give the bacteria time to adapt to the new bioload and reproduce enough to cover the new bio load without causing stress to the fish. I realize it's already too late for that but good to know for future reference. Seeing that your tank is already stocked, just be very diligent with water changes until the cycling completes. This will reduce or eliminate anymore untimely deaths. Also, make sure to properly acclimate the fish to the new tank. What I do is float the bag for a good 30 minutes or so to acclimate the temperature. Then I open the bag and slowly add water from my tank to it. Wait a bit then drain a little bit of water into a bucket and add more from my tank. I continue this for a while until the majority of the water in the bag is from my tank. This will aid the fish by slowly acclimating them to your PH and nitrate levels. Never, ever, pour the water from the lfs into your tank. You never know what is in there(bacteria, fungus, disease, etc.) and you could potentially kill your entire tank. Most fish stores have one large system where the water from all tanks cycles through them all. A fish with a disease in one tank can easily spread to fish in another tank clear across the store. This is also a good reason to have a quarantine tank for new fish before introducing them to your main tank.
I would upgrade your filter to one rated for your tank or, better yet, over rated. The current filter probably isn't moving enough water per hour around to adequately do the job. The better the water flow, the better the filtration. Just make sure to use the old filter media with the new filter as I noted above. You can also add a power head or two to help move that debris on the bottom of the tank so that it stays suspended long enough in the water for the filter to pick it up. Just be careful with the power and aiming it. Considering the sand substrate you would want to avoid a sand storm in your tank from a badly aimed powerhead or one that is way overpowered. This will also aid in tank aeration, making for better gas exchanges at the surface. Many fish will also like playing in the nice current created by the powerhead.
Lastly, make sure you give all new additions, i.e. decorations, plants, substrates, etc.(not fish) a good, thorough rinsing before introducing them to your tank, not saying that you didn't just covering all the basics. There have been countless times I've been asked to try to troubleshoot a tank issue only to find out the owner didn't clean anything before setting it up. Anything could have come into contact and contaminated them between the time of manufacturing, packaging, shipping, and storing by the manufacturer or retailer that could potentially kill the fish. A single careless employee of a retailer accidently spilling cleaning chemicals on them can have a serious impact on the entire tank.
