Best way to switch out a filter in a semi-established tank..

  • #1
HI friends,

Newbie here.. currently dealing with a fish being treated for fin rot and will be getting treated for parasites tomorrow(pet store said fine to do back to back but please comment if that is a bad idea; seems like a lot for my Rexy)... So got a lot of things going on and trying not to kill the poor little Betta. He seems to be doing a little better each day, but still not eating yet. Reason I am stating is I don't want to throw his water off anymore than it has been this past week for treatments and changes. I am just prepping for when I can upgrade his tank to a smaller new filter and get the BettaFlo Soothe starter filter out of the tank as it takes up a lot of space in there. I watched a YT video but can't find it right now..

I ordered an Aqueon QuietFow Internal 10 filter and a bunch of bio-media and sponges (fluval sponges, bio rings, and carbon bags). My goal was to use this filter media in the new filter when I replace the old- saw this video. The current filter is a carbon cartridge one, so I can't just use the existing media in the new filter. My tank is only 3.5 gallons, so not a lot of room to run two filters at the same time to get the bacteria. Please tell me the best way to transition.. I currently have the carbon catridge out of the old filter because the Furan-2 required that. Instead, I stuck a new sponge in that spot and a couple bio rings to help keep the levels normal - the ammonia was creeping up for the first time and he isn't pooping or eat (I remove the food) so not sure why.
Would I be ok if I just kept the sponge in the current filter for a couple weeks and then when I set up the new filter, use that sponge and media and call it a day? Will I transfer enough good bacteria to be safe? Thanks!
  • #2
HI Kippie. Some questions:

Looking at the BettaFlo Soothe, it doesn't look like any bio media is listed as a piece on the description page. Usually filters will have little plastic pieces that the cartridges attach to that act as a home for beneficial bacteria. Does the filter have one of these? Or is the only thing in the filter that cartridge? If the only thing in the filter is the cartridge, then that cartridge hosts most of your beneficial bacteria. Removing it basically killed your cycle (if you had one). This would likely be why you're seeing ammonia levels.

If there is nothing else in the tank housing your beneficial bacteria, you likely lost most your cycle and will have to mini-cycle the tank again. There's a chance some bacteria is holding on in your substrate and decorations, so just keep monitoring ammonia and perform water changes as you need to.

As for transitioning: If you still have the old cartridge, the best way to transfer your cycle would be to cut the whiet fiber off with scissors and stuff it in the new filter. If you don't have the old cartridge at all anymore, transfer whatever you have in your filter over if you can. Stuff it in; it doesn't have to look pretty. This will give the new filter any bacteria that is on the old one. and that's about all you'd need to do.
  • #3
Most filters that take cartridges use the cotton like outside part to both remove physical debris and house the biological filtration. The reason you are seeing a rise in ammonia is because you removed it. This removed all of your bacterial filtration and now you will have to start over cycling the tank. (Unless you have a filter designed to house bacteria in a different part, but most I've incountered don't.) Ideally you should have cut open the original cartridge to remove the carbon, and replaced the original cartridge. These filters have a fundamental design flaw and that is you are supposed to replace the cartridge monthly. That will make it so you have to start your cycle over every month unless you grow bacteria in the filter somewhere else.

As far as medications go, I would not always trust the pet store. Especially if it is a chain pet store. Their job isn't to help you, but to sell you as much stuff as possible. Over medicating is often much worse and very stressful for the fish if you are dealing with a mild problem. It is very important to make sure you properly diagnose the ailment and treat with proper medications because using the wrong meds often does more harm than good.

I would make a post here describing your fishes ailments, because I think the store may be trying to get one over on you. If the fishes only problem is mild fin rot it should heal on its own with clean water.

Also, betas don't do well if they have a lot of water current, so you can definitely over filter their water and cause stress or fin injury. Make sure this isn't occurring in your tank because it sounds like you have a lot of filtration.

I'm not sure if you know the bio balls etc that you bought will not do anything as soon as you add it to the tank. The bacteria takes weeks to months to grow. Just wanted to make sure you are aware and not confused when you get a big ammonia spike when you add the new filter.
  • #4
I agree with what TucanSam said while I was writing. The only thing I want to add is even if you have the original cartridge, it is useless if it has dried out as most if not all of the bacteria will be dead.
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  • #5
I stilll do have the cartidge but at this point, pretty sure it is dry.. If it is not(or if is and is fine), should I put it back in the tank until I cut it up to use in the new filter?

The only thing in filter is the cartridge However, the tube where the water intake is may have some in there, I did not clean it recently. For what it is worth, I am not seeing any ammonia anymore like when I tested yesterday. The only other place that may still have some is the heater because I did not clean it at all. He is hiding behind it currently. I replace one plant that was plastic with silk, so there goes any bacteria that may have been there :/

My main concern right now is he looks emaciated.. he hasn't eaten now in 1 week and 2 days.. I know they can go up to 2 weeks, but he isn't looking that great. He is not hiding all day like a few days ago though and still comes over to me occassionally. He just won't eat, looks curious like he is going to then just snubs it. I got live food, frozen food, food soaked in garlic juice.. nada. Still lots of white stringy poo still hanging. The only thing I haven't given him, was the freeze-dried bloodworms (given previously 2x/week as treats) that I think got us in this mess from making him bloated. Or is he just that picky he is willing to die LOL

Because he hasn't eaten and still looks a little bloated,I think it is parasites- hoping not dropsy.. I got seachem paraguard, but if you think it is too soon to give him it tomorrow after his partial water change please let me know. According to one aqua vet online, it can be preventive as well so it *shouldn't* harm him but given we just did the furan-2 for the whole 4 doses, I don't want to over-stress him. It is just added to the water, so maybe that is fine(?)

I am hoping to get him healthy and keep the current filter in, then I can use the white cotton from the carbon catridge to start the next. Thanks for the info in that!

Any thoughts on his anorexia?

Current water stats:

Temp- 81.1
Nitrates - 0
Nitrites- 0
Ammonia- 0
pH - 6 -6.5.. was in between
KH - 80
GH- 120
  • #6
Can you post a picture of him? It does sound like it could be parasites or some other problem. Betas don't usually go off food for that long if they are healthy. How long have you had him? I personally would give him some time to recover from the prior medication before diving right into another treatment. If he does infact have internal parasites I do not think paraguard will work since it is designed to work on ectoparasites according to the seachem website. Those are parasites that live outside the body, not inside. Their website only specifically mentions it be used to treat ich and velvet, both external ailments that you would be able to see and identify. If you want to medicate him I would select a broad medication specifically for internal parasites. The seachem site mentions a product called Metroplex and another called Focus but I haven't used either of these personally. I have only used API general cure, but I'm not positive it will work in your case. The best way to medicate for internal parasites is typically to put it in the fishes food, but that will be difficult if he isn't eating.
I would decrease the temperature to around 77F if possible. High temps can make parasites or other infections reproduce more quickly.
I hope he gets better soon. I can tell you're really trying to make him feel better and make a full recovery.
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  • #7
Thanks! I ordered PraziPro from Chewy but due to COVID-19 it couldn't tell me when it would be here Given he won't eat, I opted for Paraguard because I do think he also has fin rot and possibly(?) velvet (in the pic from a few days ago it looked a little gold near his face but I think he lost some scales from trying to squeeze between a new hideout and tank- he couldn't fit wiggled face in there). I haven't given it to him yet.

Here is a pic today after I did his 50% water change. The dorsal fine has gotten worse but its hard to say if fin rot, stress or him rubbing on the new hideout. Still won't eat, even tried te freeze-dried treats. Side note: TopFin fish accessorries are , I had to file the inside down and not every nook was 100% smooth.

He still has a long white poop hanging since yesterday. Got can see in pic too.

I reduced the temp and will reduce a little further later - didn't want to stress him by doing it too fast because he likes it warm. Let me know thoughts. Appreciate the help!


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  • #8
Wow poor dude. I think he may have a little bit of fin rot going on but it looks like most of the black is just his coloration. I don't think that is his most conserning problem. He definitely looks generally unhealthy, and probably has a lot of secondary problems originating from his parasite infestation. The paraguard may help clean out some of those secondary infections and buy enough time for you to wait for the meds that will take care of the root of the problem. He is definitely a heavily infected fish and the road to recovery will be a long one
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  • #9
Thanks! Hoping he keeps getting better little by little until I get the Prazipro. Already today I am seeing him swim more than he has in the last 1.5 weeks- so being hopeful

The metroplex can be used in the tank too and not just ingested per online.. do you think I should get that instead to have sooner than later? The local aquatics store has it in stock.. I would be able to start that in a few days vs waiting 1-2 wks for the other.

  • #10
I would try it. I've never used it but from what I've read it should work for him and it would definitely be better than waiting on shipping
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  • #11
Great thanks!

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