How to add fish to cycled tank - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 13 Old 03-11-2016, 01:12 AM Thread Starter
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How to add fish to cycled tank

My 29 gallon tank is cycled and I'm planning on adding fish tomorrow. I was thinking 8 zebra danios, 6-8 cherry barbs, and 8 bronze cories sound good. I was wondering if I should add them all at once or little by little. I've heard both but mostly little by little. I want to avoid mini cycles and if I already have enough bacteria, why do I need to add the fish slowly? Does that stock sound good? My filtration is just a sponge filter.

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post #2 of 13 Old 03-11-2016, 08:33 AM
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When it comes to adding fish it can be tricky.

That is a lot of fish but when adults all will be pretty small so you should be fine in a 29g. If it was me I would add the fish in two batches. Add the cherry barbs and about half the zebra then give the tank 5-6 days before adding batch two, I would add the cories second. I suggest water changes of 25% every day for a week after you add the fish.

The key is when you have a cycled tank you have a set amount of bacteria in the media. From what I have read it takes about 36-48 hours for that bacteria to double in size. So after adding fish it might take 3-4 days for the bacteria to catch up with the amount of fish you have. During that time Ammonia is building up so the water changes keeps things safe for the fish.

On you filter "Just a sponge filter". Sponge filters are the best bio filter you can have in your tank. You have a large surface area with lots of bacteria and even if you lose power it will keep working to keep your tank clean(not as good but better than nothing). Sponge filters aren't the prettiest thing you can put in your tank but I won't run a tank with out at least one. Most fish rooms have all sponge filters. I will say sponge filters aren't the best mechanical filtration but they do a pretty good job.

You can follow Old Fort Exotics on You Tube and on my Fish room thread.

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post #3 of 13 Old 03-11-2016, 11:14 AM Thread Starter
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Thanks warhawk. I don't want to push it with the bioload so I could have the minimum of 6 of each fish or take away the barbs all together. About the sponge filter, ya I was wondering why not everyone uses sponge filters because it seems to me that the only drawback is the ugliness (which I don't think is that bad). I guess I wrote "just" because some people have some fancy double filtration or whatever that sounds like a car or phone or something "fluval 500 360 addition with bio wheel plus" lol One more thing would it be OK to add the second wave of fish in more than a week whenever I have time? I don't see why not but just making sure.
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post #4 of 13 Old 03-11-2016, 01:57 PM
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The fish you listed are pretty small so adding 6-8 at a time would be fine. And after 3-4 days your cycle should catch up and be ready for the next batch. I like to wait a week between groups to just be on the safe side.

It took me a while to understand why sponge filters aren't used as much, here are the 2 reasons I have up with.

1- Sponge filters are old technology and people tend to think the new stuff is better.
2- Most pet stores don't sell sponge filters.

With number 1 newer doesn't always mean better, most breeders(large and small) use sponge filters because they work well, and are cheaper to run. Which brings me to number 2, the local store wants you to spend $40 on a hang on back filter and come in every month to buy cartridges for that HOB at $10-15 per month. So over a year you have spent $150 with them so they love that. Where if you bought a air pump and sponge it will cost you $20 and could last you 2-3 years. It' all about the money, they want it so they don't push the low cost filters.

I just ordered a Central air pump that will run up to 50 sponge filters for my fish room. I don't have that many but I'm getting closer every few months. The pump was $125 so a large up front cost but it is cheaper than a average canister filter and I can run all my tanks off it. Air pumps and sponges are way cheaper to run in the long run.

You can follow Old Fort Exotics on You Tube and on my Fish room thread.

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post #5 of 13 Old 03-11-2016, 04:55 PM
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I know that warhawk has given his advice already, but maybe you like to hear a second opinion?

I personally would add the fish in 5 batches. The problem is with new tanks just adding one fish can cause the ammonia to go crazy. Once it's established then its not that big of a worry. The 1st batch add half of one school, 2nd half of another school, 3rd half of the last school. Then the 4th & 5th is to increase your current schools. Doing this over a month or 2 would be great and really allow you and the filter to check your/it's self. And if you feel that the tank is too full or you don't like a particular species after all it's easier to change.

Visual representation:

1st week (4 fish from one species.. I recommend cherries)
3rd week (4 cories) <<< Or increase cherry school
5th week (4 zebras) <<< or start adding cories/increase cory school
7th week (the rest) <<< increase [cherry barb/cory/zebra] school/start adding zebras
9th week (the rest) <<< finish off all schools

But that's me. I prefer to allow the filter to reach it's max of bio filtration before adding more fish; as I believe that there is a smaller or short ammonia spike. If you add plants, they will help the filter as well!

I personally don't like sponge filters. I find them too bulky and they take up too much room in a tank. Not to mention I hate how they not as powerful as power filters, as for me air driven filters aren't as strong. Or if they are strong, the bubbles turn into a wave machine. While power filters you don't have to worry about water sloping everywhere if you decide to oversize.
Plus sponge filters are great for biological filtration; but if you need chemical or mechanical then... Power filters you can customise to suit your tastes and how you want to filter, so for me. Power filters are the way to go.
In a fish room where you might need individual tanks or for fry the sponge filters could be the better solution; but I'd stick with my powers.

Owner of fish, hermit crabs, shrimp and plants!

Hermit Crab Association (HCA) is a great resource for hermit crab care
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post #6 of 13 Old 03-12-2016, 10:42 AM Thread Starter
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Yesterday I went to get the fish and the store had lots of cool stuff but no zebra danios (just "ocelot danios" which maybe are just a strain of zebra danios like Leopard danios? They were cool but more expensive. ) I was going to get cherries but when I said that my pH was 8 (I'm pretty sure the tap water just has a bunch of minerals in it?) he said that they are hardy and I should acclimate them slowly but he seemed a little concerned. Then he suggested platies which can go up to a higher pH so I got some of those. I really don't know why I didn't plan on getting those sooner. I considered them a while ago but then I guess I forgot about them. So far I love how a small school of them fills up the entire tank. I think it would be fine with nothing else in it but I might add the cories or danios if I feel like it.
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post #7 of 13 Old 03-12-2016, 11:12 AM
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Platys are very cool. Good luck on the tank and share photos.

Austin has a good point. Given time we all learn how we like to stock tanks and stick with it. Not really sure one way is better than the other on the long run.

As for the power filters vs sponge vs canister it comes down to what you like. I have them all and I like sponges best so that's what I use.

You can follow Old Fort Exotics on You Tube and on my Fish room thread.

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post #8 of 13 Old 03-12-2016, 09:00 PM Thread Starter
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I posted a picture of the tank. It really needs more plants but $$...
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post #9 of 13 Old 03-13-2016, 03:05 AM
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Looks great. If possible, get that anubias plant and the java fern on to a piece of wood or rock. They will thank you for it; as they prefer to "anchor" on ornaments not being buried in the gravel. Not to mention, rocks/wood/ornaments will help fill up the tank and give the platies places to investigate.
If you ever want to get rid of the platies and go for fish with a lower pH, the wood is an excellent choice. The tannins in the wood help lower the pH and make the tank more acidic.

But yes, "ocelot danios" are leopard danios. It's common for a single fish to have multiple common names. For example, the guppy. Some people call them guppies others call them "million fish". Exactly the same species, just different common names.
That's why many hardcore aquarists like to use the scientific name. Each species has there own scientific name that no other species has, unlike the common name where multiple species can share the same common name.

Good luck with your fishies.

Owner of fish, hermit crabs, shrimp and plants!

Hermit Crab Association (HCA) is a great resource for hermit crab care
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post #10 of 13 Old 03-14-2016, 01:13 PM
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Stocking order and amount can be determined, in a way, by how strong the nitrogen cycle is. If your cycle is capable of oxidizing >4.0ppm ammonia in a day, you should be able to fully stock (NOT overstock) the tank all at once. If your livestock produce >4.0ppm ammonia every 24-hours, you are overstocked.

Mini-cycles are no big deal nowadays. Just test often, add Prime daily to detoxify any incipient ammonia, and change water if ammonia rises >0.25ppm or so. It only takes a day or so for the bacteria colony to double, so a mini-cycle should rarely last more than a day or two.

Sponge filters can be tamed by the addition of an airstone, which makes them more efficient as well as reducing turbulence. But a good power filter is better at removing particulates.

With a 8.0pH it's likely that your water is hard and has a high buffering capacity. How much pH lowering you might get from tannins is determined by hardness. Hard water has a very stable pH, so you might not see much action pH wise.

You can float the Anubias for shade, hides and resting places. My fish love that.
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29 gallon , bronze corydoras , filtration , stocking , zebra danios

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