In the midst of a fish-in cycle, any tips welcome.

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Aquarium Advice Apprentice
Feb 1, 2022
Colorado, USA
Hi there!

Fair warning, I'll do my best not to ramble but I'm kinda long winded and intend to be as thorough as I can. This will probably be a lengthy post. Thanks in advance for whatever time you take. :flowers:

I made an introductory post yesterday but didn't want to get quite this detailed on just an intro and I'd absolutely love any tips or insights from the more experienced aquarists on this site. I'm looking for finer points that I may have missed- I keep learning little things that I could've done better and wishing that I had someone who really knew what they were doing to point it out. Tips/critique/comments on absolutely anything that you think will help are welcome! I just want to do the best that I can for these lil' buds so I'm going to give you everything.

After a bit of a scramble I'm doing a fish-in cycle on a 20 gallon tank (15 days in, checked my receipts). I'm excruciatingly aware that this is not ideal but I'm making the most of it and so far things seem to be going as well as they can. I've done lots of reading about the nitrogen cycle and have been diligently testing my water parameters twice a day.

A rundown of how things have gone thus far:

Spouse got really excited, bought a six gallon vertical tank plus the accessories the pet store tells you that you need and way too many fish. (1 female betta, 3 albino corys, 6 ember tetras.) We set this up and had the fish for about three days while I trusted that obviously the place that sells the fish knows how to take care of them. :banghead:

I google maintenance because I want to be a good fish parent, and of course promptly freak tf out. Same day shopping spree results in a bigger tank, plus hopefully the things that I actually need.

Currently the fish are in the 20gal with a power filter, a powerhead placed near the top (and diffused with a little jerry rigged tea bag, the current was too strong but I read that the oxygenation is good for the bacteria esp. during cycling. Considering a sponge filter for it, still shopping), and a heater. (Lighting is LED hood that came with the tank.)

Substrate is dark sand and some river rock pebbles. We have several live plants, a little bit of java moss and some driftwood. The wood is from an established tank. I've counted at least six bladder snails at this point so I know that I probably have roughly five million of them in there and plan to leave them for the health of the tank (and we really like snails) but we plan to get an assassin snail if they get too out of control. I've already seen the betta try to eat one, which is nice.

I've been conditioning with Seachem Prime and changing the water basically daily (about 10-30%, depending on readings). I have the API master test kit and have kept ammonia/nitrites below 0.5ppm, today is the fourth day consecutively that the ammonia has read 0ppm/trace. Today for morning tests ammonia is zero, nitrites 0.25, nitrates 5.0ppm. Temp is 78 and ph is 7.6. (Tap water ph is about 8. Tank ph decreases slowly, usually gets to about 7.4 before water change, 7.6-7.8 after, decreases until next change.)

I ordered a bottle of Tetra Safestart which should be delivered tomorrow. This wasn't mentioned in previous articles about fish-in cycling that I read so I know this is coming late (driftwood from cycled tank has been in since the upgrade), but looking it up specifically it seems like the more nitrospiria you can inject at any time the better and I figure it can only help. Lurking on this site the past few days is actually what tipped me off. (Ty!) :)

I recently had the revelation that I should have kept someone in the six gallon and cycled both tanks simultaneously with fewer fish, as I've realized that I'm overstocked for cycling. Unfortunately information on fish-in cycling is a little sparse (most sources just tell you not to do it, which is understandable but wildly unhelpful) and I based my purchase on ideal stocking numbers under normal conditions. Now that they've been in the big one for more than a week it seems more prudent to leave them than separate them. I know that stable conditions are often more important than perfect conditions.

On saturday my gravel vac was delivered and I did a water change with it. I did a very ineffective sweep over a few scattered sand patches, not realizing that any vacuuming of substrate was inadvisable at this time. There's still lots of poop in the tank because as I say, I did a really poor job, so I'm hoping that I didn't disrupt possible bacterial colonies too much. I also wiped the insides with a sponge for the first time, like an entire doofus. Water parameters didn't do anything strange afterwards. Didn't realize the particular physical surfaces that the bacteria clung to, but I do now. I think. Maybe not the glass? I dunno. Probably the glass, too, right?


I was overfeeding at first (maybe still?), following package directions. We had some betta pellets, tropical flakes and bottom feeder pellets, I have added FD blood worms, FD brine shrimp and algae wafers.

I now usually feed twice a day (small amounts- I would feed only once but I get worried for the ember tetras as I keep seeing that they need 3x daily feedings. They're so itty bitty!) and make a point of skipping a feeding every few days. I alternate mostly pellets (coarsely ground in a pepper mill so that the tetras have biteable pieces, the betta also seems to find whole pellets too big) and flakes, giving a shrimp or worm feed every few days. Once a day in the evening I alternately drop a couple of bottom feeder pellets or a small piece of algae wafer. The corys also tend to clean up after the betta/tetras if any food drops, and I've found the amounts to feed that leave me none to cleanup after 1-3mins/2-3hrs.

I've been watching YouTube videos of stress behaviors and visible illnesses just in case, and spending lots of time watching the tank. So far everyone seems active but displaying normal behavior, everyone is eating and no one is fighting though they seem to play and hang out together pretty regularly. The betta swims up to me when I approach the tank and will follow my finger against the glass. Her colors especially seem brighter since we got her, the tetras do also. The corys are still albino, lol. The plants are popular.

As for the plants:

(Ludwigia and amazon sword, I believe, but my spouse bought these during that initial burst and I'm not 100% sure) I just made sure that they were buried in deeper piles and weighted with pebbles. The ludwigia is producing a lot of little offshoots which have made me question if I should prune it or leave it for now. I also question whether they need different substrate but figure that now is not the time to address it if they do. I used no special fertilizers or treatments of any kind for them, I've been so focused on the fish and they seemed to be doing well enough. I remove rotting leaves during water changes, but there have only been a few.

Eventually I'd like to set up the six gallon to breed a food species like the brine shrimp (It'd be nice to do something less commercially available) or do something else useful, not sure what else is appropriate for the vertical shape. We also plan to get a ten gallon tank (the 20gal came with a 10gal filter setup for some reason so we upgraded and have an extra) for something minimal (my spouse really wants guppies, maybe a small school?) and a 5 gallon just as a plant/quarantine tank. (All properly cycled well in advance of animal habitation, of course.)

Thanks for sticking with me if you've come this far! Like I mentioned I just want healthy happy fish pals so any suggestions on improving quality of life for them now or in the future are welcome.



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Well hey, good on you for reading up and catching the mistake before you ended up with a major disappointment!

You’ll find lots of varying opinions on most subjects, so take everything with a grain of salt. I think a fish-in cycle is the better way to go, of course if you have the time to monitor it closely during the process. Lots of people have issues trying to cycle a fishless tank and waiting 2 months to realize you still just have a box of uncycled water you’ve been staring at, doesn’t appeal to me lol

If you are showing declined ammonia readings and increased nitrite and nitrates you’re moving in the right direction. The cycle has started, but will take some time for it to build up a proper sized bacterial colony. Yes ideally you want to refrain from vacuuming substrate and wiping down any surfaces as there is also beneficial bacteria that grow on every surface.

I don’t think you’re overfeeding at this point in the process if you aren’t seeing ammonia spikes. That will be your first indication of overfeeding.

As for the ludwigia, I’m sure it’ll be fine in that substrate. I have it in gravel and Flourite substrates and it grows like crazy in both.
Thanks for the reply!

I'm glad to hear that someone has good opinions about fish-in cycling, every article I find online spends half of the body really emphasizing that it should only be done in emergencies if you can't return your fish. I really do get it, but man is it panic inducing and I am neurotic to my soul. Lol. Fortunately I do have the time right now and as much as I've panicked it's also been a wicked cool learning experience and has motivated me to think about larger projects in the future.

I'll leave that poop where it is for now, even though it drives me crazy. I keep looking at it when I drop the cory food like, ick, sorry guys. I guess they mind less than I do. I'll be happy to give it a good clean eventually though. And good point about ammonia spikes if overfeeding- I read that somewhere but didn't apply it to my thinking here, so thank you.

Also found a bunch snail eggs last night, like four different clusters. I'm excited about that. I know the bladder snails are considered pests, but I love them so much.
Two ways

I agree with Mer. Since you do have several fish, I would think about cutting down on the feeding because the fish will be producing enough ammonia for the continued cycle. If you were just starting, I’d recommend a couple of zebras in the tank and nothing else. They seem to be hardy when doing a fish in. It sounds like that’s not an option. Just don’t add anything else and don’t panic over an algae growth. That will handle itself once you’ve cycled or a few species that love algae will take care of most of it.
Do you think that a consistent once a day feeding is a safer bet? Maybe alternating days with less or more? I really do get a bit annoyed/worried about the amount of waste in the tank.

I know it's hard to starve the fish but I also get anxious that they're hungry while they're stressed. This might be influenced by the fact that I've had cats for decades and if they're stressed and stop eating it's a huge problem, buuuut fish are not cats and maybe my anxiety there is unwarranted. It's just a habitual response now, I guess. I'll calm that down.

I think I'll feel okay if I see a little bit of algae. It's one of the reasons I want to let the bladder snails go be fruitful and multiply, I know they'll take care of a portion of that. We were misled about the corys though, he asked specifically for something that would consume tank algae and now I see that they don't do much of that. In any case, as long as it's at a level where the concern is cosmetic and it doesn't threaten tank health I can take it, lol.

And thank you for offering your take, I appreciate the perspective.
I would just do one feeding per day. Corys are great, but think about some Siamese Algae Eaters. They’re very effective, but make sure your store knows the difference on these vs. similar algae eaters. If you’re not familiar with them, Google a photo first before purchasing. Just don’t add anything now.
I definitely won't be adding anything for a while. It looks like the Siamese AEs grow up to six inches and prefer schools, I think even one might be too much for my tank overall. If I'm going to add six inches of fish I'd prefer a small school and I was thinking about Otocinclus catfish at some point but worry that I really shouldn't add much to this tank anyway. Don't want to overpopulate once things are finally stable! I'm not sure, though. It seems like depending on who you ask I have room for anywhere from zero to ten more fish. Eh.

What I'd really love is a dwarf snowball pleco but I don't know how easy they are to find. I feel like I haven't seen any just hanging out in pet stores so maybe they're a special order kind of situation.
Edit: just searched them and see that they don't eat a lot of algae either. I still want one because they're pretty, lol
Try using the aqadvisor calculator if you haven’t already

The inch of fish rule is a pretty crude way of calculating how many fish your tank can support.

At the end of the day it’s still all trial and error as decorations can even have an impact on the bacteria in the tank. If you find that your tank can go several weeks without mandatory maintenance, and you find that snowball pleco, don’t hesitate to buy it! But on the other hand if you find yourself in a never ending cycle of maintenance and water changes, you really shouldn’t be looking at any more fish
So funny thing, my spouse just decided that he needs the vertical tank on his desk with some blue velvet shrimp. Seems like the perfect thing to put in there so we're going to start cycling it today. I suppose I could just put some shrimp in the main tank eventually, I'm sure they'll breed and we'll end up throwing the teeny ones in there as a snack. Who knows at this point, lol.

And according to that calc I'm only at 58% capacity. Maybe I should stick to shrimp for algae and fill out the schools a little, I'm sure they'll be happier that way.
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