Hi Claire and Welcome to TFF!
White haze cloudy looking water is quite normal out of the tap. It is nothing to worry about and goes away after a while. It is not the important thing to be thinking about, there are many other of those, lol! You also may see many tiny bubbles form on things and these too are harmless, they are the result of gasses like CO2 that are present in higher than atmospheric pressure and are not escaping back to the atmosphere, forming on small imperfections as small as dust (CO2 is another thing typically injected in to city water systems, just like chlorine or chloramine.)
As you may already know, the really IMPORTANT thing to be thinking about is the establishment of the all-important "biofilter" subset of your filter media that will perform the magic of constant removal of tow common fish poisons, ammonia(NH3) and nitrite(NO2) from the tank water. Since you mention cycling, you probably already are aware of this!
Since I like nothing better than to type a long-winded piece during my morning coffee, I will bore you with a repeat of the nitrogen story, lol:
When fish pump water through their gills to get that much-needed oxygen that attaches to the hemoglobin of their red blood cells, they not only simultaneously are giving off CO2, they are also directly dump ammonia(NH3) into the exiting water. This often comes as a surprise to us humans, because we don't do this (we would definately notice if people's breath smelled of ammonia, lol!) We humans, being land creatures place a much higher priority on retaining water and we have evolved elaborate kidney and bladder systems to retain water and further concentrate our ammonia before getting rid of it.
So fish are dumping ammonia to their environment more quickly (via the gills) in addition to of course also then producing waste later on which also goes directly in to the tank water. In nature, thousands of gallons of fresh water and yards and yards of swimming choices, if not miles, allow the fish gills to always find water that has virtually zero ammonia... coming in. Fresh non-ammonia water is to a fish like fresh air is to us.
Ammonia, even in tiny built-up concentrations in a contained, limited body of water is a deadly poison to fish, causing permanent gill damage and potential death. In our little tanks, these sorts of concentrations can happen within hours of something being wrong. The magic of the "biofilter" is that we grow a type of bacteria (they are an odd sort - they live attached tightly in biofilms to surfaces where they can get access to flowing water that has ammonia and oxygen from the flow - and we call them ammonia oxidizing bacteria - A-Bacs for short) and these A-Bacs like nothing better than to take small amounts of ammonia and process them in to a different substance, nitrite(NO2), which we'll talk about next. In fact, autotrophic bacteria such as these have been dubbed "eaters of rock!" In my opinion they are a huge magic of the world, another side of our world, quite opposite to all of us organic "eaters of life!"
Well, our populations of A-Bacs (currently thought to be mostly a species called Nitrosomonas spp. (but too few studies to "prove", but not really disputed)) when established in our filters are busy changing ammonia in to nitrite(NO2) and unfortunately for our fish, the NO2 is ALSO a deadly poison! But, luckily for us, along comes another world traveler called, lol, the "N-Bac." (by me, anyway.) Nitrite Oxydizing bacteria are a bunch of genetic variants thought currently to be mostly made up of a specific species named Nitrospira spp. and they like to "eat" (actually "process") nitrite(NO2) and turn it in to nitrate(NO3), a completely different substance. Nitrate(NO3) is not great but it is much less deadly to our fish than nitrite(NO2) and can be removed through a habit of weekly water changes.
So why all this bacterial science? Well, it turns out to be the KEY knowledge and skill that forms the core from which a good fresh water hobbyist builds out and adds all their other skills. Once you have some hands-on understanding about these two poisons and how to recognize and control them, you can keep your fish healthy and add other skills and extras that of course increase enjoyment. The biofilter, though not well understood in years past, has been really been the core magic helping hobbyists for decades and decades.
So we've go this aquarium heater, right? It is going to help heat up the tank to a pretty hot 84F/29C that we've found can grow the autotrophic bacteria more quickly. We'll do this for the duration of the "fishless cycle." Then, later, when the tank is ready to support fish, the heater will be adjusted down to a median temperature that is a compromise for all the different fish species you have.
We've got a filter device. It has at least four functions: water circulation, mechanical filtration, biological filtration (there's our friend
) and optional chemical filtration. We want to learn about filters, hopefully early on. The makers of filters will tell us their filter can handle thus and so size tank but of course what they are really working at is selling us the cheapest little motor and bits of plastic possible for the most money (worst case of course.) Rather than read their marketing tank size, we want to try and find (usually on their web site) the technical specs for the filter and verify that the "flow rate" in US gallons per hour or liters per hour are a certain amount. We do the arithmetic to find the "turnover rate" or the number of times per hour that the entire rough volume of our tank water is run through the filter. In most modern setups we want that to be between about 4 to 10 times and 5 is a good number we sometimes advise (we call it "5x turnover") but it's not necessarily a "better" or "best" type thing. Lower rates can be ok and heavily planted tank enthusiasts sometimes to very high rates like 10 or higher, which is usually of no concern to beginners. OK, so check and report your turnover rate, just as a little verification, it'll probably be fine.
Oh, and "mechanical" filtration means catching particles. "Chemical filtration" means all sorts of things. It's a catch-all term and the most common examples are carbon (aka activated charcoal) and Zeolite. These things are not actually needed on a regular basis in most cases (too much zeolite in particular can make it hard or impossible for your bacteria to grow!) The members can tell you the carbon story - it doesn't harm anything but is not particularly optimal in most cases.
OK, I'm beginning to get enough caffeine in my system so this is winding down and I'll leave you off to read or re-read the Nitrogen Cycle articles we have in the Beginners Resource Center: The Nitrogen Cycle, The Fishless Cycle and The Fish-In Cycle (the fish-in cycle I think of mostly as an emergency thing when beginners come in with fish, having not really learned the full cycling information yet, but it can also be used pretty effectively by experienced aquarists.) In this sub-forum of TFF we really like helping with the big basics: the Nitrogen Cycle of the "Biofilter", the "Substrate-Clean-Water-Change" core maintenance habit, the "Filter Maintenance" core habit and of course all the other freshwater tank setup and beginner things. It turns out that the month or two spent getting your biofilter up and running properly (if starting from scratch) is an absolutely wonderful time period for learning lots of the other needed things from the members and especially for beginning to learn the black art of "Stocking Plans."
Stocking Plans are the stepwise working out of a list of what species and in what quantity and which sexes of fish and in what "stockings" and at what grouping introduction times you will add your fish. In small tanks it's not elaborate, but like other things we've talked about up there, it's nice to try to learn the right stuff from the ground up. We have lots of great stockists here on TFF and plenty of enthusiastic beginners (such as myself sometimes, lol) who will give opinions and advice about how to group fish happily and how to resist overstocking a tank. Overall numbers and size, individual species numbers, species water preferences, species temperature preferences, inter-species interactions, tank dimensions and depth... oh, there's lots of stuff!
As a beginner though (just my luck if you're not really a biginner, lol), it's time to be happy that you've found a really serious hobbyist forum where there are great members who will have fun talking to you. You'll have a chance to hopefully grab a few basic skills and that first tank will be an introduction to still more fun.
~~waterdrop~~
