It's a 20 gallon. I have Indian almond leaves, I'll add them before I put in the tetras. If I can get them past the acclimation, will they be ok long term in hard water/7.0 ph?
Acclimation to me is hardest part to bringing in soft water fish into a harder water environment. Through eons of evolution they are use to and have osmotic regulators that are meant to take them from normal soft-water to a rapid influx even softer rainwater (monsoon season). They survive a drop in osmotic pressure just fine, but take that same cardinal and throw in a rapid increase in GH and TDS and they have nothing in their arsenal to deal with it. Osmotic shift upwards can be deadly or at least stun fish severely.
When you get cardinal in set bag in a water pitcher, open up bag wide open at top , use a turkey baster or bulb syringe to aerate (bubble into) the bags water to drive off any ammonia built up in bag, then after about 5min measure both the bags GH and your tanks GH so you know what kind of shift your going to get.
If your tank is higher GH be extra careful, remove a turkey baster full of water from bag, dump it into waste, replace it with same amount of tank water, wait 10min, do it again 2-3times, then about 40min later you’ll be ready to release cardinal into tank.
If you can set up a IV drip into bag of cardinals even better. The longer and slower you can make that transition from lower GH to higher GH the better.
Slow changes are always better than rapid ones regardless of which way your going in water parameters, always. That includes when your doing water changes or dosing etc, huge changes in water parameters are almost always detrimental when they happen rapidly, slow and steady wins race every time.
@Blue Ridge Reef
sig says it best, “nothing good happens in a ecosystem fast” , live it, learn it. Osmotic rupture is a bitch, plants, they melt, livestock they develop secondary infections after fins rot away from necrosis setting in, such as bacterial or fungal infection after initial osmotic shock.
Bad part is many users will say change a bunch of water when in fact all those big ass water changes with improperly prepped water are what’s causing the problem to begin with. A bad water change with improperly prepped water is worse than doing nothing to your tank, your just shocking your livestock over and over again with rapid shifts in water chemistry. Make 100% sure your change waters PH, KH, GH match your tanks waters parameters.