in line fuse is melted

im using 4ga wire with two amps one 500w for speakers and 1000w for one jl sub also a 2.0 cap the fuse was just the basic circle style that comes with install kit do i need a bigger fuse like the anl type?

If by "circle" you mean glass, then yes, I suggest any suitable "blade" type. It may have melted due to poor contacts holding the fuse. Blades are better wrt that (compared to glass & ceramic etc) but their contacts still need to be clean and firm. Check and clean every so often. If it melted due to over-current, then a bigger fuse is needed, but ensure the bigger fuse does not exceed the downstream cable it is protecting - that's a recipe for disaster (ie, fire & death). It could also be due to the inrush current of the cap though fuses might withstand that. However you can search for a few "cap" threads hereon that will tell you to get rid of the cap and improve your wiring, or install a 2nd battery - even if only a small battery (eg, 12V 1.2AH or 7AH) because they are cheaper and have far more hold-up times than caps. Your system is too small to require a cap (which is only required to protect adjacent AGM batteries in big systems (eg, >3kW), else where a 2nd smaller cap-replacement battery is undesirable).

the wire could also be too small if it isnt a true 4 gauge wire. cheap 4ga wire can be as small as a 8 gauge wire on the inside surrounded by a thick outer jacket to make it look like its bigger.

Honestly there is not enough information to give you an accurate yes or no. As stated you need to know what type of wire you are using. If it is CCA wire then you probably need to look into getting better wire. A good proper 4Ga wire will help you tremendously. As for the fuse holder you may need a bigger one but I actually prefer either the glass barrel fuse holder that you have or an ANL or mini ANL fuse holder. The fuse that you are using can also be an issue as I have seen cheaper fuses blow then melt together eliminating its usefulness. To be safe I would suggest finding out what your current draw could be. Make sure the wire you have is able to handle that. Then use the best fusing device you can afford, because lets face it if you cheap out on this piece you can either limit your current or possibly burn your vehicle down.

Noting that if the cable is of lesser quality than expected, the current should be reduced, hence the fuse last longer. That's unless the amps or loads have SMPS supplies which means a higher current if the input voltage drops. However, although high-power amps have SMPS (eg, over 200W RMS output into 1 Ohm), many don't seem seem to exhibit their typical "constant power input" behavior.