75 gallon - how much is too much

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dianak

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I am planning for stocking a well-planted 75 gallon community tank with a Fluval 405 (so a little extra power there). It is almost through cycling now and I will do this gradually but am having trouble determining what might be too much (I have seen so many different ways to calculate this). Here is what I was thinking: The small fish would be: 10 platies, 6 zebra danios, 6 corys, 6 otocinclus. The 'big' fish would be: a pair of dwarf gouramis (~3") , a pair of pearl gouramis (~4"), and a pair of angels (~6"). I would get small angels and let them 'grow into' the tank. These would be the last thing I added. Is this too much? I would like to plan on water changes every other week (barring problems).
 

Isabella

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Well, there are differing views on how to stock a tank. The most common rule is to have 1" of fish per 1 gallon of water. But I'd personally make it 1" of fish per at least 2 gallons of water. Besides: small fish like zebra danios will not produce as much waste as large fish such as angelfish or pearl gouramis. I think 10-20 fish the size of zebra danios won't produce as much waste as two adult angels, for example. You don't just consider the length of a fish, but you also must consider its body mass - the more massive the fish, the more wastes it will produce. Your plan seems fine, but I am not sure if angelfish are compatible with gouramis. What about having just the 4 gouramis and all the other smaller fish?

As for water changes, if you have a nitrate test, it will pretty much tell you how large and how frequent water changes you'll need. Good luck with the new tank. Already seems like a very pretty one (to be)
 

Skadunkadunk

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The gouramis and the angels may be ok, but im not sure about the other ones. One thing you can do is get 5 swordtails, 8 cory cats, 3 dwoarf gouramis, and 4 angelfish. As for water changes, I would change at least 10% of the water once a week. Also, what is the gph of the filter?
 

Isabella

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I really would not recommend getting 4 angelfish in one tank. If two of them pair off and start mating they may become aggressive toward the other two angels as well as toward the rest of the fish in the tank. Diana, I think you should wait for Gunnie or Butterfly to tell you what they think of mixing angels and gouramis - they really are knowledgeable.

Of course if you want, you can get the 4 angels. But just so you know: if you get a pair, they'll most likely be aggressive toward the other fish you have, including the other two angels.

As for water changes, 10% a week is just a general guideline. Every tank is different. Water changes will depend on the amount of fish you have. The more the fish and the more massive the fish - the more water changes you'll need. With a nitrate test kit you can pretty much measure how many and how frequent water changes you'll need. If nitrate is at zero or very low and increasing very slowly, it means you don't need huge and frequent water changes. If, however, nitrate is high and it increases at a fast rate after each water change, it means you need more frequent and larger water changes.

P.S. If your tank will be well planted, you'll probably not need many water changes as plants can filter the water themselves (if the plants are healthy). I do not know how it is with water changes if you use CO2 and fertilizers - I think I've heard you need regular water changes if you use CO2 and ferts (but not sure). Anyhow, a nitrate test is always good to have. As for filtration, it depends on what kind of a filter you'll have. If it is a hang on back filter, you'll need 750gph in a 75 gallon tank, and if it is a canister, you'll need at least 375-400gph of filtration - provided that water circulation is very good. The main thing is to have a filter that pumps 10 times the volume of your tank per hour. In tanks 75 gallons and up it is important to take into account water circulation - it should be good so that no water is left static and getting stagnant.
 

Gunnie

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You have received great advice so far, but my success with my tanks has been with weekly water changes of 50%. I do not have tanks with CO2 though, and I don't usually dose with ferts except for occasional tabs buried under the roots. The reason I say that weekly water changes are good is because eventhough your nitrate level might be below 10 or 20, your water still acquires a buildup of other toxins that we don't measure for on our tests. They build up in small amounts over time, and your fish adjust to these toxins until one day you have a tank of dead fish. This is called old tank syndrome. With a heavily planted, you will probably be vacuuming the gravel/substrate less than those with fewer or no plants, so keep this in mind. Fresh water added to the tank is necessary to add back trace elements lost to consumption, so this is another reason for weekly water changes. Isabella suggests 10% weekly. If it was my tank, I think I would do more than that, but that is just my opinion. Another one of our members has a beautiful large tank which I believe is heavily planted and contains discus. She must do frequent and large water changes in that tank (I think at least twice a week) because of the discus. I also believe she doses with CO2, and her tank is very beautiful and healthy. I am under the philosophy that you can't overdue it on the water changes, and more is usually better, but that is just me .
 

Butterfly

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The only thing I have to add is that your Gouramis will appreciate some floting plants. When they spawn this is where they will blow their bubble nest and subsequently spawn. Sounds like a beautiful tank. Not sure about the mixture of gouramis and angels as they both can become extremely aggressive when spawning. Good Luck and we expect pictures when it's up and running
Carol
 

Isabella

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Gunnie said:
Isabella suggests 10% weekly. 
I did not suggest 10% weekly water changes, lol. Skadunkadunk did. I just said every tank is different and she'll see for herself how many and how frequent water changes she'll need. I personally would not suggest 10% weekly water changes, which is why I replied she'll see how many and how frequent water changes she'll need. I myself normally perform 30% weekly water changes in my 30 gallon tank, and with 2 adult angels and 11 sizable-sized baby angels in my 30 gallon tank as of now - I perform 50% water changes twice a week.

I also agree on doing at least small regular water changes in a planted tank to add trace elements present in water as nutrition for plants, as well as to remove various toxins/elements/compounds accumulating over time that we cannot measure with test kits.
 

Gunnie

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Isabella said:
Gunnie said:
Isabella suggests 10% weekly. 
I did not suggest 10% weekly water changes, lol. Skadunkadunk did. I just said every tank is different and she'll see for herself how many and how frequent water changes she'll need. I personally would not suggest 10% weekly water changes, which is why I replied she'll see how many and how frequent water changes she'll need. I myself normally perform 30% weekly water changes in my 30 gallon tank, and with 2 adult angels and 11 sizable-sized baby angels in my 30 gallon tank as of now - I perform 50% water changes twice a week.

I also agree on doing at least small regular water changes in a planted tank to add trace elements present in water as nutrition for plants, as well as to remove various toxins/elements/compounds accumulating over time that we cannot measure with test kits.
Sorry Isabella!  I didn't read your post properly.  Sorry.   
 

Isabella

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It's OK Gunnie I thought you might have confused my post with that of Skadunkadunk. The reason I replied was just in case, to clarify that I personally wouldn't recommend as small as a 10% water change a week. With the fish Diana is planning to have (the larger gouramis and angels) she'll most likely need larger water changes. Plus, she'll need trace elements for plants. Unless someone has a large tank with very very small amount of some small fish, usually larger water changes than 10% a week are better.
 

Butterfly

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In my 75 gallon I do 25-50% water changes each week, but then the fish in there are real poop machines
Carol
 
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dianak

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Re: 75 gallon - followup question

Thanks for all the good advice! I think maybe I will forego the angels, since I really want this to be a community tank and don't want anybody taking over. Another question: I would like to get one or two pairs of gouramis, but don't particularly want them to breed. From what I've read, you don't really want multiple male gouramis together because they'll fight. If I put a pair in a community tank, would this pretty much discourage them from breeding? Can they be happy just to hang out without making whoopy? If not and I got one or more males, would they be lonely?
 
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