Sounds to me from reading  that Sterazin is formaldehyde and either methylene blue or malchanite green with it.
What ever it is, it won't bother the beneficial bacteria in your tank , however it will stain your tank so be careful when dosingthat you don't spill it!
Also, you can use an oral antibiotic with these ingredients.
Andrea, I really think you should try it and see if there is an improvement. 

Andrea, I'd use the medication with Malachite Green, Methylene Blue and Formaldehyde ASAP. And combined with Melafix. It is mostly used to cure a wider range of paracites / protozoen including ich.

(Talking about tetracycline, my fish guy mentioned he doesn't believe in its strenght anymore because most of bacteria on this earth are allready immune to it)  but we wanna treat first against paracites.

Minde, we cannot get oral medication here in Australia.

I asked the fish guy about that one too and he said even medication used in water will treat internal infections because fish live in water and the meds get inside their body anyway.

Andrea, please keep us updated. Big hugs for you and I know you do the very best you can. Blow a fishy kiss for Sunshine 

I brought those tri-sulpha tablets, I really didn't have much choice. They had Sera products but not the one Nossie mentioned, none of their medications actually, just their water conditioners etc.

I did not find anything with tetracycline in it, but the guy recommended this after looking at the photos. I also added more of the bactonex to the water which contains the meth... blue stuff. I also brought some stability, I will do a water change in 3 days and add that plus stress zyme. It says to re-dose in 3 days if there is no improvement. However, if there is no improvement I will switch to the sterazin. If there is any sign of improvement I'll stick with the tablets. I have no melafix left, could I use the pimafix instead?

I've decided there is a severe lack of treatments around me for fish, I have very little choice which is just plain s.h.i.t!

Sunshine was acting really bad this morning but has acted fine since I fed her which was a couple of hours ago.

I will keep a very close eye on my water quality and just wish for the best.

Hanna and Andrea,
Sulfa is a antibiotic and you can soak your pellets in it and then feed them to Sunshine.
You can also at the same time treat for parasites with the sterazin the petshop reccommended.
You may not be able to get the oral fish food antibiotics but you certainly can create your own.
The oral antibiotics that I used and also the ones Nossie used have sulfa in them.
I guess I wasn't making myself clear or there was a miscommunication on this.

I'm not going to use that sterazin unless there is no trace of other products in the water. It strictly says to do that so it must be for reason! Why else would it say not too?

Soaking the pellets in the sulfa is a great idea though

I have no experience with tetracycline but I've read a lot about it being recommended against all kinds of bacterial infections, and if I remember it correctly, it could be used both as a water treatment, and even more effective, as injected into the fish.

Either way, I'd completely skip the Melafix, why add something that won't help in any way when there's already medication in the water? I'd rather have it as an after treatment as well. Either way, do please keep us updated on Sunshine's progress
My, I can't understand how she could've gotten so sick suddenly

Phew, this is good to know Minde, big thankies for the info

Well Sunshine is a big fish so you would want to give him more.
I crushed about 3 pellets and fed those to Cali 2 X's a day and also fed her  reg. pellets mixed with tetracycline 1X's per day.
so she got three feedings a day total.

ANDREA,  I  AM  WORRIED  How are thing s going, Hope our darling Sunshine is on the mend.
Big hugz for you.

Sorry I haven’t been around, I’ve been a bit stressed out and confused with all the advice being thrown at me. Not that I don’t appreciate it, I can’t express how much I appreciate all of your help!!

Now so I treated with the tri-sulpha tablets externally on Sunday, I also soaked some pellets in it Sunday afternoon and Monday morning, but neither were any help. It actually got worse and Sunshine seemed very sick. I went to a concert on Monday night and for some reason I expected to come home to a dead fish  I don’t think it was that bad though and well obviously it wasn’t as Sunshine is still alive and kicking (or should I say swimming?).

I didn’t know where to go next, I went back to the fish shop and told the expert person there that I should have talked to from the start, about it all. Well he pretty much agreed with you Mindemae about the red pest and well I am pretty sure that is right. So I am currently treating with Bio-Tet by aquasonic (Link is not visible to guests. Please register to view.)
Now it appears I have unfortunately messed up the treating a bit.

I found this out because I am cheating on you guys with another forum  Haha This is what they said about tetracycline

“Tetracycline is deactivated by light, if the water color turns from yellow to dirty its off, is more toxic and wont work anymore. High gh and ph reduces effect and you need to higher the dose. But with about 6.6mg/l you should be alright, hoping your gh is not too high. Dose daily for a week with at least 25%water change prior each dose. If the water turnes brownish or so go up to 80%”

My water is currently yellow. I am waiting on their reply about should I dose the whole tank again or just the water changed. The person is from Australia which always helps. The marks are still there but some have healed and have hope that this is going to work, I just feel like this is it and we will all beat it together  Sunshine seems happier, I’m just annoyed with myself for messing the treatment up a bit.

I had ammonia present yesterday, so I did a water change, added both stability and stress zyme, I am now also using stress coat by api as a water conditioner. Then I treated with the bio-tet.

I will follow this persons instructions, would you have anything to add on to it?

I have nothing to add since I'm not familiar with this treatment I do hope Sunshine will get better And I hope she's not too stressed about all the different medicines!

Good luck and keep us posted

Thanks Nossie and Minde. I hope she isn't too stressed either, I haven't been able to sleep as I've been so worried Sunshine is my baby and I feel so bad letting her get so sick, especially when I've been trying to do everything right for her by getting the bigger tank and learning as much as I can. I feel like such a failure of a fish owner.

My ph is 7.6 so hopefully that isn't too high. When you treated, did you treat the whole tank every day too Minde? I'd thought you'd suggest I could soak the food in it, will do

Yes I know that now  Major mistake on my count!! I give up on fish shops, why didn't the bloody fish guy tell me  I'm soo p.i.s.s.e.d off with them!!

I'll tell you why the fish guy didn't tell you that...point blank...he didn't know himself.

Good to hear!

I really hope you won't have to have sick fish anymore either!! But as long as you'll keep doing what you're doing with all that love and care, they'll all be great