This is normal and is needed for bottle carbonation. What you are seeing is natural yeast sediment which has settled to the bottom of the bottle while clearing.
Handcrafted beer contains the natural yeast sediments, these are harmless, but you may not enjoy drinking it.
If you want to ensure your beer is clear when serving;
- Decanter your bottle of beer into a serving jug first. Pour so as not to disturb any of the yeast sediment at the bottle.
- Then pour the beer from the serving jug.
Alternatively, if you have space in a refrigerator when fermentation has finished put your fermenter into a fridge just before bottling. The cold temperature will allow all the sediment to drop to the bottom, then you can syphon the beer off the top into bottles and you will dramatically reduce sediment in your final beer.