Male female ratio

Question
1. Currently filling a 55 gallon tank.
2. I only have a male fancy tailed guppy and three platys one female two male. I plan on getting a molly and some tetras this weekend.And I inquired earlier about adding a female betta to the tank. Not sure I'll do the Betta just yet though.
3. Not sure how to describe filtration. Cant remember the name of the filter right now but it is made for a fifty five gallons and successfully made it through four turtles I one kept so it is pretty sufficient I think. I do a partial water change once a week. And do a complete change once a month along with filter changes most of the time.
5. Dont really know how old the tank is it is pretty old about five six years maybe.

Hi, I'm wondering if the general rule to have more female than male always applies. the platys I have seem seem to get along fine so in their case should I add females? I think one of the males may not be that old. He is the same size as they are he just is not as plump but it could be because he is a different kind maybe. I plan on getting a molly but don't really want to deal with ten million babies in the tank and since I already have the platys whom I presume will be giving birth to many I was thinking of just getting a female or a male. I know the female may already be pregnant when I get her but I can deal with it a few times I just dont want to do it all the time. I will probably just leave them (fry)in the same tank and do a strong will survive type thing anyway but their so hard to catch and doing the changes of water with them in there is so hard!!! So is it okay to get just a female or just a male or will they never be happy that way.

2. Same question for my male guppy. He already bugs the other fish A LOT. I'm considering taking him back and trying another guppy. Or will this behavior stop if I get a few females for him. He is driving the fish crazy as I'm typing this. I heard they could be a little bothersome sometimes just a mark of the species maybe? What should I do with him?

SOOOO confused please help. Thanks so much.

Answer
Hello!

With platies you should get 1 male for every 2 females, but it is not always needed. It is a good idea though.

However, with guppies you MUST get 3 females to every male, or no females at all. Guppies are nice but they sure can be annoying little things. The behaviour will not stop, but it will spread out a little. I think he would like it more with 3 or 4 females.

Also, the ratings on the filters are for super understocked aquariums. The general rule of thumb is to double the recommendation. For example, if you have a 20 gallon tank, get a filter recommended for a 40 gallon, if you have a 55 gallon tank, get a filter rated for 110 gallons.

Good idea leaving the fish in the tank. If you have a lot of hiding places some should survive. It is the best thing to do unless you plan to sell the fry. Occasional fry are good nutrition for some fish anyways.

-Nick