Do I need special water conditioners for my fish tank?

The best way to keep the water clear is to use water changes, a testing kit, and keep it away from windows. Sometimes even that is not enough and instead of spending a lot of money adding prodcusts like AlgaeFix that may or may not work on your tank (it didn't on mine) you could buy a UV filter. Now, UV filters cost a lot of money but imagine how much you would be putting into buying algaefix if it decided to only work if it's added every day? Not only that, but UV filters can also filter out other things like diatoms (brown algae) and parisites in your tank. I think they are well worth the buy.

You need to be using something to make your water safe for fish. AquaSafe is a good choice. I would not use anything that removes ammonia, nitrite, or nitrate unless your tap water has a high level of either three. I also would not add anything that supports the bacteria (or bacterial filter) in your tank. That may cause the cycle to crash if you skip a dosing of the stuff.

So, you want something that removes chlorine and heavy metals, but not anything that helps cycle, adds bacteria, helps the bacterial filter, detoxifies ammonia, nitrite, or nitrate.

As long as the tank stays around 70 degrees, that tropical fish is fine with the goldfish.

Make sure you buy a test kit (ammonia, nitrite, nitrate tests are important to have.) and test weekly. While goldfish can survive rediculously poor condiotions, catfish cannot. So, you need to keep ammonia under 0.25, nitrite under 0.25 and nitrate under 20. You do this with at least 25% water changes every week. If that does not seem like it's enough do two 25% water changes or more a week.

Never change the filter in the tank. That's where all of the bacteria that eat ammonia and nitrite live. If it gets clogged rinse it out in a bucket of tank water and put it back. I recommend buying a filter that gives you options for what you want to use to filter the tank (filter media is the short word for that.) AquaClear is a well known brand for that. They use a foam peice, a carbon packet, and something to promote bacteria growth. All you do in that filter is replace the carbon every month.

Also, make sure your filter has at least a 160 GPH turnover, the larger the better. To get that GPH you may need to buy a filter that is for a 40 gallon tank or more. Goldfish are messy fish.

Umm Goldfish are cold water and what Species .Fancy Goldfish can live in a 20 to 30 gallon tank but common/comet would need at least 75 gallons .

the cat fish should not be in with the Goldfish either .

You should of been using something already to make tap water safe like Aqua safe or prime .

tap water contains chlorine and some tap water contains Chloramine which are both fatal to fish .It also removes heavy metals as well in the tank water .

Green water is Algae caused by to much sunlight High Nitrate and Phosphate and over feeding.

Tanks once cycled for 4 to 8 weeks in the first place do not need cycling again .

You need a water conditioner that removes chlorine and chloramine. There are many different products that do this (they will say so on their labels). Other than that, goldfish need no special water amendments.

Chemicals that are supposed to rid an aquarium of algae either don't work or do more harm than good.

Don't overfeed your fish and the alge should stay away.

Stop wasting money and buying addictives, instead, do weekly water changes. Use a clean cloth or an algae scrubber and remove the algae every week when you're doing maintenance, you might have too much light or leave your light on for too long, make sure your tank is alway from direct sunlight. Have a decent filter that filters 5x your tanks capacity per hour. Lastly you might have way to much nutrients inside your tank so avoid over feeding. If you're lazy and don't maintain your tank, you're going to get algae for sure. But if you use these tips, you most likely wont have any.

Yes, using Tap water conditioners is good to remove chlorine and chloramines from water.

But you should also do water test time to time to have an eye on water ecological balance and nutrients that cause algal bloom.