Plants and water changes

[BenAquatics]

I recently watched an Aquarium Co-Op video where Cory mentioned that his indoor breeding ponds don't need water changes because his plants absorb waste.

 

Before watching that video, I've heard that fry need very clean water to grow. It's not unusual to hear about fishkeepers doing 50% water changes 2-3x/week on fry growout tanks. I've also heard elsewhere that we need to do water changes because fish release growth inhibiting hormones. Is this a myth?

 

If I keep my planted tanks lightly stocked, provide enough lighting, and test my water regularly to verify there is no ammonia/nitrites and minimal nitrates, can I get away with minimal water changes?

Edited August 8, 2021 by BenAquatics

[lefty o]

you can potentially go a very long time with minimal maintenance. plants are excellent filters. i really doubt the growth inhibiting hormone theory. sounds like wives tale horse manure.

[KBOzzie59]

Very clean water maybe yes/maybe no.  I had a recent spawn of pepper corys, at 5 weeks old I put 2 back in the tank with the parents.  It is a heavily planted 20 long with a large population.  The rest are now in a 5 gallon tank.  They were all hatched in a Fluval breeder box on the 20 long. The 20 long normally just gets water top offs and a water change of about 30% every couple of months.  The 5 gallon gets 50% every other day.  The juveniles in the 20 long are about 1.25" the group in the 5 gallon are right at 1", the 5 gallon gets fed 4 times a day, the 20 long only once a day.  

[Guppysnail]

On 8/8/2021 at 6:11 PM, BenAquatics said:

fish release growth inhibiting hormones. Is this a myth?

Yes and no. Not growth inhibitors but stress hormones these translate to a stress reaction in other fish as group defense mechanism in the wild to avoid predation.  In our tanks it doesn’t wash away. It keeps fry on high alert burning calories “worrying” and paying more attention to surroundings than eating causing slowed growth.  Sometimes stunted if it’s a lot of stress hormones and dominance display hormones 

[HH Morant]

I think my ex-wife gave off stress hormones!

[Odd Duck]

On 8/8/2021 at 5:25 PM, lefty o said:

you can potentially go a very long time with minimal maintenance. plants are excellent filters. i really doubt the growth inhibiting hormone theory. sounds like wives tale horse manure.

I ended up with waaaaaayyyy too many Jack Dempsey fry and was doing massive, frequent water changes to keep the parameters from reaching toxic.  The largest of the fry would grow just fine and the smallest would barely grow at all, even when I made very certain everybody got adequate food.  When they get spread out among more tanks with more elbow room but very similar water parameters, they would put on big growth spurts.

I’m not saying I’m convinced it was growth inhibitors (I’ve never looked for, or read any, studies about it).  But I wouldn’t be shocked if it were true.  Plants and corals certainly are known to produce substances that inhibit growth of other surrounding plants/corals.

I have no idea if there were actually growth inhibiting hormones swirling around, if I really wasn’t getting adequate food to the smallest, if the smalls were burning more calories getting chased, or any number of other factors that could play into this scenario

Just a few thoughts on it.  There probably won’t be any studies on it since hormones like that are potentially species specific.  The only species that might get studies are going to be food fish that are farmed.  They already have studies on stocking densities, so it’s unlikely that anybody will fund a study to even find out if a actual growth inhibiting hormone exists.

[GardenStateGoldfish]

On 8/8/2021 at 6:11 PM, BenAquatics said:

I've heard that fry need very clean water to grow. It's not unusual to hear about fishkeepers doing 50% water changes 2-3x/week on fry growout tanks

This is really all about water quality, some breeders do that and feed very heavy, I breed goldfish myself, and my outdoor tubs of goldfish fry get no water changes, green water keeps the water perfect for fast growth and the fry eat the green water, it keeps levels at 0,0,0. My indoor tubs I keep a ton of elodea in to help with waste, but I still gotta do a water change once a week or every other week. The green water is amazing though. 
 

tldr it’s all about water quality

[Torrey]

I thought I grabbed the quote questioning growth inhibiting hormones, apparently I did not. 

 

There is a plethora of research on the effects of gamma-aminobutyric acid and somatostatin functioning as growth inhibitors in fry, and the lasting impacts of stunted growth.  Some of the research is open access, a lot is behind paywalls.

Most indoor breeders will do daily 50% water changes (I did a 50% 2x a day with my Zebra Danio fry, just like I did when I bred discus), and feed 4x day to capitalize on growth. 

https://pubmed.ncbi.nlm.nih.gov/19735661/

[BenAquatics]

Thank you for all the responses! 

[Torrey]

On 8/11/2021 at 11:41 PM, Torrey said:

I thought I grabbed the quote questioning growth inhibiting hormones, apparently I did not. 

 

There is a plethora of research on the effects of gamma-aminobutyric acid and somatostatin functioning as growth inhibitors in fry, and the lasting impacts of stunted growth.  Some of the research is open access, a lot is behind paywalls.

Most indoor breeders will do daily 50% water changes (I did a 50% 2x a day with my Zebra Danio fry, just like I did when I bred discus), and feed 4x day to capitalize on growth. 

https://pubmed.ncbi.nlm.nih.gov/19735661/

There's a link here to a pubmed article on growth inhibiting hormones in fish and how they function. 

Apparently, depending on browser, there may be issues opening the link. It's NIH article /19735661 if you have to manually search it

[Water Box Dreams]

With regard to water changes I have a plant tank which appears to have reached equilibrium. After almost a year of weekly 50% water changes and liquid fertilisers it appears the tank doesn't need me anymore. No fish in it only plants. Never cleaned it - allowed the mulm to build up and feed the plants. There is visible mulm in it but its not a huge build up. Haven't done a water change or fertiliser in 2 months, only top up the evaporation with rain water. Very little almost no growth going on anymore, but all the plants are healthy. Time will tell. Theoretically I should just need to provide light and heat in winter.