I’ve got a 10 gallon fresh-water tank that previously was home to a beautiful betta. He died about two weeks ago.
I knew that I’d likely get some more fish, so I haven’t taken the tank down. We’ve decided to get some guppies next. I’m curious about whether or not I need to do a complete or partial water change before I re-stock the tank.
I’ve got an undergravel filter, but I’ve also got a tank vacuum which I’m planning on using again before we put new fish in, and there are still some small snails in the tank. I’ll check the pH, but is there anything else I need to do to prepare the tank? I’ve set up new tanks many times, but I’ve never re-stocked a tank before (when the fish died we just took the tank down.) I’ve also read that guppies like 1 tbsp. of salt per 5 gallons. Can I just add the salt to the water? Is there anything special I need to do?
Well, first I would get yourself a water test kit and check the water to make sure it wasn’t something in there that killed Beta.
Then, assuming the water is ok, clean the gravel with your vacuum and you should be fine.
I would start slow - maybe 5 guppies - then once they are established you can add about another 4 - 5.
They’ll breed if you get the conditions right - then you can get a special fuzzy fake plant for the babies to hide in (Lest mumma and daddy eat them.)
Oh - add the salt when you do water changes - mix it in with the fresh (and make sure to get aquarium salt - table salt will NOT work).
Also, the test kits are inexpensive and very easy to use.
Thanks, Alice! Yeah, I’ve already got a test kit, and I’m pretty sure the betta just died of old age (we’d had him for a few years). I had guppies as a kid, and we’ve still got one of those little containers for pregnant fish with the slots in the bottom – so I’m good to go if/when I get a momma guppy.
I’d dreaded doing a whole water change, so it’s good to know that a good vacuum should suffice. How often do you need to re-add the salt? I’m going to go ahead and mix some in after the vacuum, but after that how often do I need to check the salinity?
Thanks for your help!
You should never add more salt. When you lose water due to evaporation, the salt stays in the tank.
That’s also why you shouldn’t allow the tank to become too low on water. It will increase the salinity.
Ya, what Slip Mahoney said 
Just want to add though that salt isn’t necessary. I’ve raised guppies just find without salt. Now, I wasn’t trying to bread them so that may make a difference.
The only time to add salt is when you do a water change. You should do a partial water change regularly. If you are keeping salt in the tank you should add enough to make up for the water you removed. Slip Mahoney was right though about not adding salt to water added for evaporation.
Tannim’s got it right - when you remove water from the tank (as in YOU remove the water - it doesn’t evaporate) at a smidge more salt.
The helps prevent fish stress - non-stressed fish are more likely to breed. I used to have a breeding pair of sevrums (Freeda died :() The little fishies would die instintaniously without salt in the water.
Interestingly, sevrums make very good parents - the babies will swim between the back fins of both mommy and daddy - it’s really cute.