Topic: Is it safe to keep guppies with mollies? I have a 30 gallon aquarium with molly fish and I was wanting to add some guppy fish. With the two live together fine without too many issues? What is the worst case scenario? I need some help.

*Awarded Answer
Posted by Kelsey B: Your a good fishkeeper for reaching out and doing research like this. Props on you! Hopefully your fish tank goes well for you. Lets answer your question now.

Keep Guppy Fish with Molly Fish?

A molly fish and a guppy fish will live together just fine. The worst case scenario is that the mollies become a little more aggressive than the guppies and they chase them until they get severely stressed out and maybe die. The male molly can get pretty aggressive when there is females in the tank. One way you can cut down on stress is to add a bunch of plants. You can use fake or real. I just bought this kit and love it. Here is a picture and link:

So my one male guppy is absolutely obsessed with my marble molly. He follows it everywhere…. this has been going on for well over 2 weeks… has anyone witnessed this before?

Looking for a decent sized fish to go in my 35 hex. I’ve done the guppy, Molly, tetra small schooling fish thing. want something different. Any ideas for that size tank?

45 hex you might be able to do a small gourami like a honey gourami. But because the hex is tall and not very long it is hard to put anything other than what you have already done in it. You could do a betta and some tetras.

Help, one of my loaches died along with 2 of my ghost shrimp my water parameters are all good I just feel like my ph is high at 8.8 consistent even after water change using prime all my other fish are fine (guppy, molly, gourmi, rainbow).

I’ve tried lowering but nothing happens I did a 50% water change today and used prime for the dechlorinator and the ph is still 8.5 and up ph out of my tap is 7.6

This is the substrate I have about 50-55lb of it in a 55 gallon tank, could that be a problem I have so much since i have live plants.

Have you made any changes lately? Like adding stuff into the tank? Rocks or even maybe chemicalish product like plant fertilizer.

Yes! I added plant fertilizer (seachem flourish excel) I also added a plastic decor but have since took all plastic decor out and only have live plants.

For shrimps… they prefer stable water parameter if you add stuff like that it will raise the TDS and will shock them if high dose.

Just do your water changes and add that driftwood in then you should be fine. I see your video the water circulation isn’t strong if you added the Seachem Flourish Excel and all the chemical stayed on the bottom that why loaches and shrimps got killed? –I think–

One last question, could the reason my ph rises in my big tank and not my small tank be because I have a lot of black sand in the big tank and just colorful gravel in the small one ph difference between them is 7.6-8.6

You can but I wouldn’t change it all at once. There’s still some good bacterial in your substrate so you should do it day by day. OR if you love sand then I think you can go for pool filtered sand. I heard it’s really cheap and doesn’t affect pH.

My other small 5 gallon tank which I have moved all my other loaches and shrimp has been consistent at 7.5, I don’t know why the ph in my new big tank has been so high.

What do you have in your tank? pictures? and first of all.. fish wouldn’t die even high in ph unless it’s a swing, but shrimp will because they’re extremely sensitive to changes.

If your water parameters came back ok. It could have been a parasite etc. The list goes on. I would just keep an eye on the other fish.

I added the purigen to my canister filter today in the morning, driftwood is no longer in tank but water is almost back to normal.

Got a question. Rescued some guppy and molly fry about a couple months ago, had to put them in the breeder to avoid being eaten by the parents. The guppy fry are growing, albeit slowly, should be big enough to release in another few weeks to a month. The molly fry however is still very tiny. She eats plenty, swims fine, no deformities that I can tell… even her color is good. She just isn’t growing. Water temp is around 78, water conditions are good. Feeding them crushed flakes and fry growth food with plenty of veggies. Is there anything I’m missing?

What do you mean by breeder? One of the small ones that hang or suction to the inside of your tank? Or like a breeder tank like a 10 or 20g? What I learned with fry is that if they are kept in a small net/breeder box for too long they tend to grow really slow…. the bigger the tank the faster they grow. My first round of fry I ever had stayed small for so long cuz I was afraid to let them out of the breeder box in fear of them being eaten… my next round I caught momma and placed her in a 5g and put momma back when she was done and they ended up bigger than the older fry in no time so I quickly put them all in an even bigger tank. Plus I fed them flakes and frozen brine shrimp 2-3 times a day.

Small one inside tank. I can step up the feedings, no spare tank and about 12 other fish in the tank. I was just puzzled as to why the guppies grew but not the molly.