Question

fish fam! Welcomed six gorgeous fish to my tank today and I've been totally mesmerized watching them for an hour straight. Big plans ahead - adding 9 more finned friends in just a couple of weeks! Also getting a spacious 150-gallon tank(2nd tank) with an advanced FX4 filter too – it's on its way!

Now, here's where you come in – I'd love your expert advice! Whether it's suggestions for fish that'll thrive in my bigger tank or tips on maintaining my aquatic oasis, drop your pearls of wisdom below. Consider yourselves my fishy mentors! Let's dive into this fin-tastic journey together!
what fish should I get next ?

Food

To give useful advice we would need to know your water parameters such as PH, ammonia, nitrites and nitrates. GH and KH levels would also help. The thing is that different fish thrive in different water types. For instance South American cichlids are going to want softer water while many/most live bearers want harder water.

GH and KH can usually be found on the web site for your water company. Ammonia and nitrites are controlled by cycling your tank to build up good bacteria. The bacteria colonies convert ammonia to nitrites and then nitrites to nitrates. Cycling is the first essential step in setting up an aquarium. Fish produce ammonia through urine as does decaying left over food. Ammonia, along with nitrates are both toxic and should be at zero PPM (Parts Per Million). Nitrates can also be toxic but to a much lower level. A reading of anything less than 20 PPM is usually OK. Live plants help with nitrates but this is normally controlled by not over feeding and water changes. I suggest the API Master test kit for checking all but KH and GH. As to cycling here is an excellent article kept on this site.

You must also 'condition' your tap water to remove chlorine which is very toxic to fish. I use API Tap Water Conditioner. There are also other good products for this but just stay away from any that contain aloe Vera such as Stress Coat as the aloe Vera remains suspended in the water and, over time, will decrease the fish's gill function.

As to the food I've never used Omega One but it seems to have a good reputation. TetraMin and Bug Bites are also good options. Again, as with other considerations, it depends a lot on the fish.

Sorry if I've gone too deep on this post but what I've said is important and you used the word 'Beginner' in your handle.

How long has the tank been set up for?
Has the filter been cycled (developed colonies of beneficial bacteria that convert ammonia into nitrite, and nitrite into nitrate)?

Don't add anymore fish until the tank has cycled (assuming it isn't already).

Tiger barbs need to be kept in groups of 10 or more to stop them killing everything in the tank, including each other.

Not sure if you have a picture on the back of the tank but all aquariums should have a backing of some sort. You can buy aquarium backings from pet shops or online, or use coloured card or a plastic bin liner. Just tape them to the outside on the back of the tank.

Try and avoid having red, blue or purple light on by itself, it's not natural for the fish. Standard white light is best.