what is going on with my tank?

Hi. Welcome to fish keeping. Some mistakes often made by new'er people. I'm no pro, but I've been in it a little while.

You shouldn't change the filter media so soon. Especially if your still in your cycle. Your filter keeps the bacteria that you've been trying to grow during the cycle. Depending on how much was on there you may end up seeing another cycle again. Keep all the decor and gravel in there as these also contain the bacteria you need.

The couldiness is the bacterial bloom. This is normal. Some people get it some people don't. It could go away over night it could go away in a week. Just be patient. It shouldn't bother the fish any.

The brownish algae is probably from the nitrate that is showing up as it seems you are nearing/were nearing the end of your cycle. You could check your water for phosphate too as this will contribute to algae. Your snails should be able to work on some of this. How close is your tank to sun light or how often/long do you have your light on?

What type of filtration are you using? If you're using a UGF, thoroughly vacuuming can really disturb the biological bacteria. Even if you're not using a UGF, some helpful bacteria will build up on your gravel, so you might want to vacuum gently, getting the debris up with minimal disturbance to the gravel; try not to turn it under / really mix it up.
As stated, you want to be careful about changing your filter media. If you need to, you can always remove some of the water from the tank and rinse the media out in that water, this will help to clean out the debris and disturb the growing bacteria far less than removing and replacing part of the filter.
If your ammonia is 0 you're well on your way through the cycle, be patient, keep up the water changes to keep the nitrite levels down, and soon you'll have a clear, cycled tank and very happy fish

This sounds like what happened with my first fish, a male betta in a 10 gallon(well I built up to the ten anyways), and you're having the same problems I did. The cloudy water is exactly what I had! I freaked out even worse then you did and heat sanatized the whole tank hence killing the cycle and the betta in the end. I really had no clue what I was doing back then. Some times in a cycle you get a grey or white bacteria bloom. It's ok and shouldn't hurt the fish it just makes the tank look bad. It's not the bacteria you need for your cycle but from what I've come to understand it thrives under the water conditions you get during a cycle. It'll pass and clear up, maybe do afew extra water changes to clear it up faster, might help. The algea can be cleared up by watching how long the tank is exposed to light. Also I had a small bloom of brown algea in my current tank but it was localized on one tank decoration. I just washed it under hot water and haven't had it return yet (I was lucky maybe). You'll want to keep the tank decorations, fake plants and filter media, in the tank until the cycle is done though. THe good bact that you are growing is on the surfaces in the tank NOT in the water. If you can replace what you took out put it back ASAP you might be able to salvage what ever was on it. Relax limit the light to the tank to keep the algea down and watch the nitrAtes for that as well since nitrAtes are fertilizer for plants. I hope things clear up soon just watch and wait the first cycle is really a pain but you can learn ALOT while it's happening. All I can really suggest is doing more water changes. Try daily changes to get over this part of the cycle. It may seem like a pain now but I promise you once you hit full cycle and you only do one a week you'll enjoy it. God knows I am!
-Neo Sithlord

It is a mistake to think that vacuuming a UGF removes or somehow damages the bacteria responsible for nitrification - it does not.

With conventional flow UGF, it is supremely important to get the mulm out of the gravel or it will suffocate the bacteria. Nitrification bacteria are quite firmly attached, vacuuming will not dilodge them - else FBF could not work could they - those are being vacuumed 24/7.

Untended UGF (not vacuumed well and regularly) do not work well for long periods, they clog and become time bombs.

Actually now that you mention the emperor (w/bio-wheel) it makes a world of difference. Most the bacteria you need will be on the bio-wheel so throwing away the filter media won't make too much of a diff. Personally I'd keep it there as it may provide more places for the bacteria to colonize. The more oxygen rich places you have for colonization the faster it should cycle. Thats all and done for I guess but still shouldn't make too much of a difference if any at all. Just don't do anything to the bio-wheel!! lol

Cleaning the gravel won't do anything towards the negative. That is unless you have super deep gravel with stagnant air thats been trapped for a while and you decide you're going to stir it up.

You can scrub off the algae or not it doesn't make a difference to you cycle. Now knowing that you have the bio-wheel you probably didn't do too much to effect the cycle.

Just to let you know you probably could leave the filter pad in there for a very long time as long as you rinse it out every once in a while. The only real purpose of the filter pad is mechanical filteration. The carbon in there doesn't really last long and eventually turns from chemical filteration to biological filteration.

All you really need carbon for is
1. aid in the removal of medication
2. aid in the clearity of the water (i.e. removing tannins from driftwood)
3. aid in the clearing up of a stench

You shouldnt have to worry about any of these unless you have a sick fish that NEEDS medication, put in drift wood, or don't clean the tank in a while.

BIO WHEEL! WOOT! ermm well that changes things. You should be ok then. I've done my research on filters and anything with a bio wheel ranked at the top for a "hang on back" / "HOB" filter. I'm still learning myself and I'm afraid of changing my filter "pad"/"floss" unless I really have to. I've rinced it in the tank water I drain out for my weekly water change but I do so very carefully. Again I'm new to this and very tenetative about changing things, but I'm "well read". I tried to keep my water at 0 ammonia (I jump started this part of the cycle via a partial fishless I'd suggest aiming at .25 ppm with a fishy cycle), .25 max for nitrItes and 20 ppm nitrAte. I've come to think that if you can read ammonia and nitrItes you have more then enough "extra" to feed the bact that you have established in the tank and continue to grow what you will need to fully cycle. When you read ZERO in ammonia and nitrItes you have enough bact to keep the tank healthy and hence fully cycled. It's just alot of water changes to get to that point! Again I love it now. I added afew fish at a time every week or two after that and didn't notice any major spikes.
Don't worry about the what you've done so far just keep at it and keep reading/posting. Once you finish the whole cycle you'll really get into the fun part of keeping fish as pets. As with everything in life take it one step at a time, You're doing fine.
-Neo SIthlord
One last thing doesn't sound like you have an under gravel filter (UGF) so vacuming the gravel shouldn't effect anything.Achronynms on these boards take a while to get down we really need a sticky for those!

As far as the brown algea, With a Fish only tank, algea is a constant issue IME, Light and excess nutrients are all that algea needs to grow well. KMy Fo tanks always had some algea, but If I missed maintenance, they went nuts. Reduce your light to only the time you are viewing the tank, and up your water changes. strip the nutrients (ammonia, nitrate, phosphate) out of the water via maintenance and you will see the algea reduce or go away. Something else to bear in mind is that during the estabilishment of a new tank there is usually a lot that goes on that will stabilized in time, so don't get discouraged.