Salt used as treatment for fin rot – can it cause constipation?

Salt used as treatment for fin rot (pics) – any negative side effects?

Hello!
So my little boy Merlin got fin rot and is now recovering. Here's the story if you want to skip it and go directly to the question, it's the separate paragraph titled QUESTION at the bottom (above the "additional info" paragraph).

I've had him since March 27 (he was given to me by my sweet boyfriend), and he was the healthiest betta in the store. I've been keeping an eye on the bottom of his tail since it looked like he had fin rot in the past that he recovered from, since his tail structure was slightly different on the bottom, so I thought he might be prone to getting it again sometime. But he's only been getting healthier since I got him, he's perked up quite a bit, his color has deepened and he's an active and happy boy. So out of the blue, this Monday I wake up to see the bottom of his tail fin in tatters! I had taken a picture of him the night before (see first pic), and his fin had been fine. I was horrified, and that's when I took the second picture (the closeup). Immediately I got to work sterilizing a gallon jar to use as a hospital tank, put conditioned temperature adjusting water inside, and proceeded to walk an hour roundtrip to PetSmart to buy some aquarium salt (since I was stranded at home without a car until the evening). I got home, dissolved the aquarium salt, transferred my little boy via a fishnet, and turned off the lights and left him alone for a half hour to let him calm down. When I checked back, he was swimming happily and curiously around as if nothing had happened So I then proceeded to clean his old tank and that's when I noticed (!!!!) that he had done a big poop the night before inside his little cave that I made for him, which he sleeps in every night, SO HIS TAIL HAD BEEN RESTING ON THE POOP ALL NIGHT. Lovely. That's why his fin rot progression had been so dramatic. Phew, now at least I knew the cause.

(QUESTION So anyhow, long story short, every day since I've been taking a picture to show his healing progress (the last picture is from today) and I do say his tail is healing quite wonderfully, especially since it's only been 4 days Problem is, I have yet to see a single poop on the bottom of his hospital tank, even though I've been feeding him his regular amount (5 NLS pellets every day, except for today, I've only fed him 3), and he still attacks the pellets like he's been starved for weeks (he'll jump out from the water and eat the pellets off my finger ). I'm not exactly sure what his personal bowel movement schedule is, but I do know that when I rinse his substrate every week, I do find some presents in there left for me Should I be worried that he hasn't had a BM yet even though I've been feeding him regularly? I guess my main question is, does aquarium salt cause constipation? Is the salt stressful for bettas even though its used in small amounts? What are any possible side effects? And how long can I leave him safely in the salted hospital tank, should I keep him in there (water changes of course) until he's completely recovered? I have read conflicting info on the effects of salt for betta fish. All I know is that his tail is healing amazingly fast, he hasn't pooped yet, and he is still swimming actively and happily. In fact, he made a big bubble nest only the day after I moved him Usually it takes him an extra day or two after a water change before he starts. And I don't think he has a bulge in his belly area yet but I'm not sure... so yeah, I'm just wondering if the salt will cause constipation, how long it is safe to leave him in there, and if I should continue to add a pinch of it into his tank water when he's back to normal like I had originally planned (since the salt is labeled "for freshwater fish" and says it improves gill function, balances electrolytes and promotes disease recovery.

UPDATE May 6: He made 2 big poops last night!! So constipation isn't an issue! However, I'm still wondering about all the other questions I asked about the longterm effects of salt on him. Also, I just did a 100% water change and took an update pic which is now at the bottom of the post

Thank you for any help!!!

Additional info:
•Tank size: 1 gal.
(yes I know this is way too small for a betta, but I can't afford a larger tank and it's just out of the question for a number of other reasons, so it won't be of use if you suggest I upgrade since I already know I should and I want to, but I can't. Just putting that out there so I try to make up for it by doing weekly 90% water changes and washing his substrate.)
•Water change: 90% weekly, 20% every 3 days
(I don't have water stats since I can't afford the test kits either, but I try to make up for it by doing frequent water changes! and I do know about the nitrogen cycle, so since I don't have a cycled tank I try to keep the water changes flowing)
•Water temp (heated): 78*F
•Filter: no
•Feeding schedule: 2 NLS Betta pellets in the morning, 1 midday, 2 at night
•Water conditioner used: Aqueon Betta Bowl Plus (I just bought Prime so I won't be using that any more in the future)
•Plants in tank: Marimo moss ball

(yes... it did take me ages to get a good picture of him... he's insanely active so you can imagine how hard it was, color editing helps though to keep the photo exposure consistent! )

(May 1) Evening before, no damage:



(May 2) Closeup of fin rot damage, Day 1:



(May 2) Day 1:



(May 3) Day 2:



(May 4) Day 3:



(May 5) Day 4:



(May 6) Day 5:

 

Welcome to Fishlore, hope you get some responses today

 

Should I be worried that he hasn't had a BM yet even though I've been feeding him regularly? Yes. If it goes on for much longer you can try an Epsom Salt bath or feeding him a cooked and skinless pea.

I guess my main question is, does aquarium salt cause constipation? Yes.

Is the salt stressful for bettas even though its used in small amounts? What are any possible side effects? Yes. They are freshwater fish which means they are adapted to very low concentrations of salts in their environment. They still need it but the concentration in their outside environment relative to what's inside their bodies affects how easily they can maintain proper cell function and osmotic pressure.

And how long can I leave him safely in the salted hospital tank, should I keep him in there (water changes of course) until he's completely recovered? How much salt did you use and what volume is the hospital tank? For a salt bath you should only leave him in for 15 minutes. If you're treating his home tank with a very low dose then you're supposed to be able to leave him in it.

 

Thank you so much for your reply, Aquaphobia! I will try your suggestions in the future if I have any more problems. Thankfully, he had a huge BM on Friday, and so far every day since he's gone a small amount regularly. I've kept him in the salt-treated water for a week now, 1/2 rounded tsp. aquarium salt to 1 gal. water (I did a 100% water change half way through). As of today he's officially totally healed from the fin rot, and on Tuesday I will be moving him back to his regular tank, because that's when I pick up his weekly amount of water from a semi-local underground spring. He is still just as active and curious as always and appears to be very healthy and energetic. Should I continue to add aquarium salt to his water since he's done so well with it? Should I lower the dose or keep it the same? Or should I just not add any at all?

 

I would stop adding it, or perhaps reduce it slowly over time just in case he's become used to it and can't readjust as quickly back to fully fresh water.

 

Thank you for your quick reply! I'll will slowly decrease the amount. I think the cause of his temporary constipation was just the stress from going totally salt-less to salt-treated water, so I don't want to make him go through that again now that he's readjusted.

On a lighter note, I included a link to a video I took of him today his blue is so pretty, and he's such an active and curious little guy