Surprise Baby Platys

I had to do the same with my v. platies, I put the male into another tank to avoid too many offspring. 

Do you have plans for getting a bigger tank at some point in the future? Ever?

If not, go with the 106. But if there is any chance of upgrading, get the 206. You can regulate the flow on these filters so the 206 would be OK.

Molly fry are quite big for fry, but if you find they are at risk of being sucked into the filter, cover the end of the tube that takes water out of the tank. The preferred method seems to be a cube of sponge with a slit cut in it slid over the end of the tube, but even a knee high sock tied on (the things that look like the bottom chopped off a pair of tights) would do the job - that's what I used in my 50 litre to stop baby shrimps getting sucked in.

Upgrading to larger tanks is something I've done a few times over the years - 60 to 125 litre, then 125 to 180 litre. It is easier to do if the bigger tank is not going in the same place as the smaller tank but it is still do-able if it's going in the same place. The secret is planning in advance. If you know what you are going to do and have everything ready before you start, it won't take nearly so long and the fish won't get as stressed.
With a bigger tank it is so tempting to rush out and fill it with more fish, but you do need to take it slowly or the bacteria won't cope.
Rather than go through it all now, let us know when an upgrade is imminent and we'll talk you through it.


When you get the external, the simplest way to change filters is to put all the media from the current filter into the external and fill the gaps with new media. A bit in each basket would seed the new media faster. Wait a month, then remove a bit of the old media, replacing it with new media that you had to leave out. Wait a month, then replace a bit more. And so on till all the old media has gone. You will lose the bacteria on the the casing of the old filter but there are lots more all over the tank. Just keep an eye on the ammonia and nitrite levels for a few days, and again every time you remove a bit of old media to be on the safe side - and do a water change if you do get a reading above zero.

It is impossible to say how long a fishless cycle will take, there are just so many variables. Anything from 4 weeks to a couple of months.

However, because you already have a tank with a mature filter you can speed things up quite a bit by taking up to a third of the media from the current tank and placing that in the new filter. If you change to an external before getting another tank, I would suggest waiting till all the old media is removed from the external, or maybe get a new tank just before you remove the last bit of old media so you can use that to seed the bigger tank's filter.